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Authors: Gerhard C. Rossouw, Ryan Orr, Dale Bennett and Ian S. E. Bally.
Functional Plant Biology (2024)
Abstract: "Reproductive development of fruiting trees, including mango (Mangifera indica L.), is limited by non-structural carbohydrates. Competition for sugars increases with cropping, and consequently, vegetative growth and replenishment of starch reserves may reduce with high yields, resulting in interannual production variability. While the effect of crop load on photosynthesis and the distribution of starch within the mango tree has been studied, the contribution of starch and sugars to different phases of reproductive development requires attention. This review focuses on mango and examines the roles of non-structural carbohydrates in fruiting trees to clarify the repercussions of crop load on reproductive development. Starch buffers the plant’s carbon availability to regulate supply with demand, while sugars provide a direct resource for carbon translocation. Sugar signalling and interactions with phytohormones play a crucial role in flowering, fruit set, growth, ripening and retention, as well as regulating starch, sugar and secondary metabolites in fruit. The balance between the leaf and fruit biomass affects the availability and contributions of starch and sugars to fruiting. Crop load impacts photosynthesis and interactions between sources and sinks. As a result, the onset and rate of reproductive processes are affected, with repercussions for fruit size, composition, and the inter-annual bearing pattern."
"Regulation der Korngröße bei Weizen entdeckt"
Quelle: Pflanzenforschung.de (12.03.2024)
Durch Ausschalten des TabHLH489-Gens mit der Genschere CRISPR/Cas erhöht sich die Körnergröße und Ertrag von Brotweizen.
Auszüge: "Weizen ist die weltweit bedeutendste Getreideart nach Mais und die Erntemenge beträgt ca. 800 Millionen Tonnen im laufenden Wirtschaftsjahr 2023/24. Um die Versorgungssicherheit für die weiterwachsende Weltbevölkerung zu gewährleisten, sind in den kommenden Jahren deutliche Ertragssteigerungen notwendig. Chinesische Forscher haben dazu einen neuen Ansatz gefunden. Durch Genom-Editierung mit der Genschere CRISPR/Cas konnte das Team Weizenvarianten erzeugen, die höhere Erträge liefern. Im Fachmagazin Plant Biotechnology Journal erläutern die Forscher:innen, dass das Gen TabHLH489 eine Schlüsselrolle für die Korngröße spielt."
"Das Ausschalten des Gens für TabHLH489 und seinen homologen Genen mittels der Genschere CRISPR/Cas führte zu einer Zunahme der Kornlänge und des Korngewichts, während die Überexpression zu einer Abnahme beider Werte führte. Darüber hinaus konnten sie einen ganzen Regulationskomplex aufdecken: TaSnRK1α1, die α-katalytische Untereinheit des pflanzlichen Energiesensors SnRK1, interagierte mit TabHLH489 und phosphorylierte den Transkriptionsfaktor, um seinen Abbau zu induzieren und so die Entwicklung des Weizenkorns zu fördern. Eine Zuckerbehandlung induzierte ebenfalls die Anreicherung des TaSnRK1α1-Proteins und führte so zu einer Senkung des TabHLH489-Proteinspiegels..... Auch Brassinosteroide steuern die Korngröße - Darüber hinaus konnten die Forscher:innen zeigen, dass das Pflanzenhormon Brassinosteroid (BR) die Kornentwicklung fördert, indem es die TabHLH489-Expression über den Transkriptionsfaktor BRASSINAZOLE RESISTANT1 (BZR1) verringert. Eine weitere wichtige Beobachtung war, dass natürliche Variationen in der Promotorregion von TabHLH489 die BZR1-Bindungsfähigkeit beeinträchtigen und dadurch die TabHLH489-Expression beeinflussen. Insgesamt konnte die Studie damit den grundlegenden Regulationsmechanismus für die Korngröße bei Weizen aufklären: das TaSnRK1α1-TabHLH489-Regulationsmodul, das auch BR- und Zuckersignale integriert. Damit steht nun der Weg offen, gezielt Weizensorten mit erhöhter Korngröße und Ertrag zu züchten."
Authors: Jinyang Lyu, Dongzhi Wang, Na Sun, Fan Yang, Xuepeng Li, Junyi Mu, Runxiang Zhou, Guolan Zheng, Xin Yang, Chenxuan Zhang, Chao Han, Guang-Min Xia, Genying Li, Min Fan, Jun Xiao and Ming-Yi Bai.
Plant Biotechnology Journal (2024)
Abstract: "Regulation of grain size is a crucial strategy for improving the crop yield and is also a fundamental aspect of developmental biology. However, the underlying molecular mechanisms governing grain development in wheat remain largely unknown. In this study, we identified a wheat atypical basic helix–loop–helix (bHLH) transcription factor, TabHLH489, which is tightly associated with grain length through genome-wide association study and map-based cloning. Knockout of TabHLH489 and its homologous genes resulted in increased grain length and weight, whereas the overexpression led to decreased grain length and weight. TaSnRK1α1, the α-catalytic subunit of plant energy sensor SnRK1, interacted with and phosphorylated TabHLH489 to induce its degradation, thereby promoting wheat grain development. Sugar treatment induced TaSnRK1α1 protein accumulation while reducing TabHLH489 protein levels. Moreover, brassinosteroid (BR) promotes grain development by decreasing TabHLH489 expression through the transcription factor BRASSINAZOLE RESISTANT1 (BZR1). Importantly, natural variations in the promoter region of TabHLH489 affect the TaBZR1 binding ability, thereby influencing TabHLH489 expression. Taken together, our findings reveal that the TaSnRK1α1-TabHLH489 regulatory module integrates BR and sugar signalling to regulate grain length, presenting potential targets for enhancing grain size in wheat."
Authors: Morgan Vanderwall and Joshua M. Gendron.
Development (2023)
Summary: HEXOKINASE1 is a crucial regulator of plant development. In this Spotlight, we discuss the vital role of HEXOKINASE1 catalytic activity and glucose-6-phosphate production in plant growth and senescence.
Abstract: "As photoautotrophic organisms, plants produce an incredible spectrum of pigments, anti-herbivory compounds, structural materials and energic intermediates. These biosynthetic routes help plants grow, reproduce and mitigate stress. HEXOKINASE1 (HXK1), a metabolic enzyme and glucose sensor, catalyzes the phosphorylation of hexoses, a key introductory step for many of these pathways. However, previous studies have largely focused on the glucose sensing and signaling functions of HXK1, and the importance of the enzyme's catalytic function is only recently being connected to plant development. In this brief Spotlight, we describe the developmental significance of plant HXK1 and its role in plant metabolic pathways, specifically in glucose-6-phosphate production. Furthermore, we describe the emerging connections between metabolism and development and suggest that HXK1 signaling and catalytic activity regulate discrete areas of plant development."
Authors: Javier A. Miret, Cara A. Griffiths and Matthew J. Paul.
Journal of Plant Physiology (2024)
Abstract: "Sugar homeostasis is a critical feature of biological systems. In humans, raised and dysregulated blood sugar is a serious health issue. In plants, directed changes in sucrose homeostasis and allocation represent opportunities in crop improvement. Plant tissue sucrose varies more than blood glucose and is found at higher concentrations (cytosol and phloem ca. 100 mM v 3.9–6.9 mM for blood glucose). Tissue sucrose varies with developmental stage and environment, but cytosol and phloem exhibit tight sucrose control. Sucrose homeostasis is a consequence of the integration of photosynthesis, synthesis of storage end-products such as starch, transport of sucrose to sinks and sink metabolism. Trehalose 6-phosphate (T6P)-SnRK1 and TOR play central, still emerging roles in regulating and coordinating these processes. Overall, tissue sucrose levels are more strongly related to growth than to photosynthesis. As a key sucrose signal, T6P regulates sucrose levels, transport and metabolic pathways to coordinate source and sink at a whole plant level. Emerging evidence shows that T6P interacts with meristems. With careful targeting, T6P manipulation through exploiting natural variation, chemical intervention and genetic modification is delivering benefits for crop yields. Regulation of cereal grain set, filling and retention may be the most strategically important aspect of sucrose allocation and homeostasis for food security."
Authors: Linhui Zhu, Yuwu Liao, Kai Lin, Wenfei Wu, Lanjuan Duan, Pan Wang, Xian Xiao, Tingting Zhang, Xin Chen, Jianzhong Wang, Kaiqin Ye, Hao Hu, Zeng-Fu Xu and Jun Ni.
Tree Physiology (2024)
Abstract: "Anthocyanins are flavonoid-like substances that play important roles in plants in adaptation to various environmental stresses. In this research, we discovered that cytokinin (CK) alone could effectively induce the anthocyanin biosynthesis in Eucalyptus and many other perennial woody plant species, but not in tobacco and Arabidopsis, suggesting a diverse role of CK in regulating anthocyanin biosynthesis in different species. Transcriptomic and metabolomic strategies were used to further clarify the specific role of CK in regulating anthocyanin biosynthesis in Eucalyptus. The results showed that 801 and 2241 genes were differentially regulated at 6 and 24 h, respectively, after CK treatment. Pathway analysis showed that most of the differentially expressed genes were categorized into pathways related to cellular metabolism or transport of metabolites, including amino acids and sugars. The metabolomic results well supported the transcriptome data, which showed that most of the differentially regulated metabolites were related to the metabolism of sugar, amino acids, and flavonoids. Moreover, CK treatment significantly induced the accumulation of sucrose in the CK-treated leaves, while sugar starvation mimicked by either defoliation or shading treatment of the basal leaves significantly reduced the sugar increase of the CK-treated leaves, and thus inhibited CK-induced anthocyanin biosynthesis. The results of in vitro experiment also suggested that CK-induced anthocyanin in Eucalyptus was sugar-dependent. Furthermore, we identified an early CK-responsive transcription factor MYB113 in Eucalyptus, the expression of which was significantly upregulated by CK treatment in Eucalyptus but inhibited in Arabidopsis. Importantly, overexpression of EgrMYB113 in the Eucalyptus hairy roots was associated with significant anthocyanin accumulation, and upregulation of most of the anthocyanin biosynthetic genes. In conclusion, our study demonstrates a key role of CK in the regulation of anthocyanin biosynthesis in Eucalyptus, providing a molecular basis for further understanding the regulatory mechanism, and diversity of hormone-regulated anthocyanin biosynthesis in different plant species."
Authors: Zobaida Lahari, Sarah van Boerdonk, Olumide Owolabi Omoboye, Michael Reichelt, Monica Höfte, Jonathan Gershenzon, Godelieve Gheysen and Chhana Ullah.
New Phytologist (2024)
Abstract: "Strigolactones (SLs) are carotenoid-derived phytohormones that regulate plant growth and development. While root-secreted SLs are well-known to facilitate plant symbiosis with beneficial microbes, the role of SLs in plant interactions with pathogenic microbes remains largely unexplored. Using genetic and biochemical approaches, we demonstrate a negative role of SLs in rice (Oryza sativa) defense against the blast fungus Pyricularia oryzae (syn. Magnaporthe oryzae). We found that SL biosynthesis and perception mutants, and wild-type (WT) plants after chemical inhibition of SLs, were less susceptible to P. oryzae. Strigolactone deficiency also resulted in a higher accumulation of jasmonates, soluble sugars and flavonoid phytoalexins in rice leaves. Likewise, in response to P. oryzae infection, SL signaling was downregulated, while jasmonate and sugar content increased markedly. The jar1 mutant unable to synthesize jasmonoyl-l-isoleucine, and the coi1-18 RNAi line perturbed in jasmonate signaling, both accumulated lower levels of sugars. However, when WT seedlings were sprayed with glucose or sucrose, jasmonate accumulation increased, suggesting a reciprocal positive interplay between jasmonates and sugars. Finally, we showed that functional jasmonate signaling is necessary for SL deficiency to induce rice defense against P. oryzae. We conclude that a reduction in rice SL content reduces P. oryzae susceptibility by activating jasmonate and sugar signaling pathways, and flavonoid phytoalexin accumulation."
Authors: Blanca Jazmin Reyes-Hernández and Alexis Maizel.
Current Opinion in Plant Biology (2023)
Abstract: "Lateral root (LR) formation in Arabidopsis is a continuous, repetitive, post-embryonic process regulated by a series of coordinated events and tuned by the environment. It shapes the root system, enabling plants to efficiently explore soil resources and adapt to changing environmental conditions. Although the auxin-regulated modules responsible for LR morphogenesis and emergence are well documented, less is known about the initial priming. Priming is characterised by recurring peaks of auxin signalling, which, once memorised, earmark cells to form the new LR. We review the recent experimental and modelling approaches to understand the molecular processes underlying the recurring LR formation. We argue that the intermittent priming of LR results from interweaving the pattern of auxin flow and root growth together with an oscillatory auxin-modulated transcriptional mechanism and illustrate its long-range sugar-mediated tuning by light."
Authors: Taras Pasternak, Stefan Kircher, Klaus Palme and José Manuel Pérez-Pérez.
Planta (2023)
Main conclusion: Root development is regulated by sucrose and light during early seedling establishment through changes in the auxin response and chromatin topology.
Abstract: "Light is a key environmental signal that regulates plant growth and development. The impact of light on development is primarily analyzed in the above-ground tissues, but little is known about the mechanisms by which light shapes the architecture of underground roots. Our study shows that carbohydrate starvation during skotomorphogenesis is accompanied by compaction of nuclei in the root apical meristem, which prevents cell cycle progression and leads to irreversible root differentiation in the absence of external carbohydrates, as evidenced by the lack of DNA replication and increased numbers of nuclei with specific chromatin characteristics. In these conditions, induction of photomorphogenesis was unable to restore seedling growth, as overall root growth was compromised. The addition of carbohydrates, either locally or systemically by transferring seedlings to sugar-containing medium, led to the induction of adventitious root formation with rapid recovery of seedling growth. Conversely, transferring in vitro carbohydrate-grown seedlings from light to dark transiently promoted cell elongation and significantly reduced root meristem size, but did not primarily affect cell cycle kinetics. We show that, in the presence of sucrose, dark incubation does not affect zonation in the root apical meristem but leads to shortening of the proliferative and transition zones. Sugar starvation led to a rapid increase in lysine demethylation of histone H3 at position K9, which preceded a rapid decline in cell cycle activity and activation of cell differentiation. In conclusion, carbohydrates are required for cell cycle activity, epigenetics reprogramming and for postmitotic cell elongation and auxin-regulated response in the root apical meristem."
Authors: Kang Du, Wenqing Zhao, Zhiwei Lv, Lin Liu, Saif Ali, Binglin Chen, Wei Hu, Zhiguo Zhou and Youhua Wang.
Physiologia Plantarum (2023)
Abstract: "In maize, young kernels that are less competitive and have poor sink activity often abort. Studies have indicated that such poor competitiveness depends, in part, on the regulation by auxin (IAA) and abscisic acid (ABA). However, the mechanisms for such effects remain unclear. We used pollination-blocking and hand-pollination treatments accompanied by multi-omics and physiological tests, to identify underlying mechanism by which IAA and ABA, along with sugar signaling affect kernel development. Results showed that preventing pollination of the primary ears reactivated kernels in the secondary ears and altered both sugar metabolism and hormone signaling pathways. This was accompanied by increased enzyme activities in carbon metabolism and concentrations of glucose and starch, as well as increased levels of IAA and decreased levels of ABA in the reactivated kernels. Positive and negative correlations were observed between IAA, ABA contents and cell wall invertase (CWIN) activity, and glucose contents, respectively. In vitro culture revealed that the expression of genes involved in glucose utilization was upregulated by IAA, but downregulated by ABA. IAA could promote the expression of ABA signaling genes ZmPP2C9 and ZmPP2C13 but downregulated the expression of Zmnced5, an ABA biosynthesis gene, and ZmSnRK2.10, which is involved in ABA signal transduction. However, these genes showed opposite trends when IAA transport was inhibited. To summarize, we suggest a regulatory model for how IAA inhibits ABA metabolism by promoting the smooth utilization of glucose in reactivated young kernels. Our findings highlight the importance of IAA in ABA signaling by regulating glucose production and transport in maize."
Authors: Woei-Jiun Guo, Benjamin Pommerrenig, H. Ekkehard Neuhaus and Isabel Keller.
Journal of Plant Physiology (2023)
Abstract: "Endogenous programs and constant interaction with the environment regulate the development of the plant organism and its individual organs. Sugars are necessary building blocks for plant and organ growth and at the same time act as critical integrators of the metabolic state into the developmental program. There is a growing recognition that the specific type of sugar and its subcellular or tissue distribution is sensed and translated to developmental responses. Therefore, the transport of sugars across membranes is a key process in adapting plant organ properties and overall development to the nutritional state of the plant. In this review, we discuss how plants exploit various sugar transporters to signal growth responses, for example, to control the development of sink organs such as roots or fruits. We highlight which sugar transporters are involved in root and shoot growth and branching, how intracellular sugar allocation can regulate senescence, and, for example, control fruit development. We link the important transport processes to downstream signaling cascades and elucidate the factors responsible for the integration of sugar signaling and plant hormone responses.
Authors: Stefan Kircher and Peter Schopfer.
Current Biology (2023)
Editor's view: Kircher and Schopfer show that photosynthetic sucrose produced in the leaves acts as phloem-mobile signal controlling lateral root formation and root elongation in a synchronized manner. These results provide an outline of the molecular pathway through which light affects photomorphogenesis in plant parts that are not directly reached by effective light.
Highlights • Photomorphogenic and photosynthetic photoreceptors are involved in light signaling • Photosynthetic sucrose, not auxin or HY5 protein, acts as a shoot-to-root signal • Sucrose-induced auxin biosynthesis in the root tip drives the lateral root clock • Auxin controlling lateral root formation is synthesized from tryptophan
Abstract: "The development of plant roots is subject to control by light. Here, we show that, similar to monotonous root elongation, the periodic induction of lateral roots (LRs) depends on the activation by light of photomorphogenic and photosynthetic photoreceptors in the shoot in a hierarchical order. The prevailing belief is that the plant hormone auxin serves as a mobile signal transmitter, responsible for interorgan communication, including light-controlled shoot-to-root connections. Alternatively, it has been proposed that the transcription factor HY5 assumes the role as a mobile shoot-to-root signal transmitter. Here, we provide evidence that photosynthetic sucrose produced in the shoot acts as the long-distance signal carrier regulating the local, tryptophan-based biosynthesis of auxin in the LR generation zone of the primary root tip, where the LR clock controls the pace of LR initiation in an auxin-tunable manner. Synchronization of LR formation with primary root elongation allows the adjustment of overall root growth to the photosynthetic performance of the shoot and the maintenance of a constant LR density during light-dark changes in a variable light environment."
Authors: Francois Barbier, Franziska Fichtner and Christine Beveridge.
Nature Plants (2023)
Editor's view: This Review summarizes recent knowledge and offers new insight about the role of strigolactone signalling in the integration of nutritional and metabolic status, as well as its consequences for plant development and architecture.
Abstract: "Strigolactones are rhizosphere signals and phytohormones that play crucial roles in plant development. They are also well known for their role in integrating nitrate and phosphate signals to regulate shoot and root development. More recently, sugars and citrate (an intermediate of the tricarboxylic acid cycle) were reported to inhibit the strigolactone response, with dramatic effects on shoot architecture. This Review summarizes the discoveries recently made concerning the mechanisms through which the strigolactone pathway integrates sugar, metabolite and nutrient signals. We highlight here that strigolactones and MAX2-dependent signalling play crucial roles in mediating the impacts of nutritional and metabolic cues on plant development and metabolism. We also discuss and speculate concerning the role of these interactions in plant evolution and adaptation to their environment."
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Authors: Muhmmad Asad Ullah Asad, Zhang Yan, Lujian Zhou, Xianyue Guan and Fangmin Cheng.
Plant Physiology and Biochemistry (2024)
Highlights: • Sugars play an essential role in the regulations of leaf senescence. • Abiotic stresses trigger sugar signaling by inducing reactive oxygen species burst. • Sugar signaling interact with plant hormones and protein kinase to regulates leaf senescence. • Abiotic stresses target sugar signaling to regulate photosynthesis inhibition and programmed cell death (PCD).
Abstract: "Plants have evolved the adaptive capacity to mitigate the negative effect of external adversities at chemical, molecular, cellular, and physiological levels. This capacity is conferred by triggering the coordinated action of internal regulatory factors, in which sugars play an essential role in the regulating chloroplast degradation and leaf senescence under various stresses. In this review, we summarize the recent findings on the senescent-associated changes in carbohydrate metabolism and its relation to chlorophyll degradation, oxidative damage, photosynthesis inhibition, programmed cell death (PCD), and sink-source relation as affected by abiotic stresses. The action of sugar signaling in regulating the initiation and progression of leaf senescence under abiotic stresses involves interactions with various plant hormones, reactive oxygen species (ROS) burst, and protein kinases. This discussion aims to elucidate the complex regulatory network and molecular mechanisms that underline sugar-induced leaf senescence in response to various abiotic stresses. The imperative role of sugar signaling in regulating plant stress responses potentially enables the production of crop plants with modified sugar metabolism. This, in turn, may facilitate the engineering of plants with improved stress responses, optimal life span and higher yield achievement."
Authors: Robert Maple, Pan Zhu, Jo Hepworth, Jia-Wei Wang and Caroline Dean.
Plant Physiology (2024)
Abstract: "Plant species have evolved different requirements for environmental/endogenous cues to induce flowering. Originally, these varying requirements were thought to reflect the action of different molecular mechanisms. Thinking changed when genetic and molecular analysis in Arabidopsis thaliana revealed that a network of environmental and endogenous signalling input pathways converge to regulate a common set of ‘floral pathway integrators’. Variation in the predominance of the different input pathways within a network can generate the diversity of requirements observed in different species. Many genes identified by flowering time mutants were found to encode general developmental and gene regulators, with their targets having a specific flowering function. Studies of natural variation in flowering were more successful at identifying genes acting as nodes in the network central to adaptation and domestication. Attention has now turned to mechanistic dissection of flowering time gene function and how that has changed during adaptation. This will inform breeding strategies for climate-proof crops and help define which genes act as critical flowering nodes in many other species."
Authors: Aehsan ul Haq, Sumira Farooq, Mohammad Lateef Lone, Shazia Parveen, Foziya Altaf and Inayatullah Tahir
Journal of Plant Growth Regulation (2024)
Abstract: "Postharvest senescence of cut flowers is a stumbling impediment in harnessing their commercial potential. Consequently, the postharvest quality preservation of cut flowers is a crucial factor to allure buyers and maximize economic gains. Flower senescence being final phase of organ development is a key factor triggering postharvest quality deterioration. The process of flower senescence is closely regulated by developmental and environmental cues. The perception of these signals subsequently involves loss of membrane integrity, decreased activity of antioxidant enzymes, and upregulation of proteases and nucleases, which are key signatures of senescence and culminate in the death of petal tissues. Moreover, the developmental and environmental cues are synchronized by considerable turnover in different growth regulators, particularly cytokinins, abscisic acid, ethylene, and gibberellic acid, which act both antagonistically and synergistically to coordinate the senescence process in flowers. Among these growth regulators, ethylene has a crucial role in orchestrating petal senescence in ethylene-responsive systems, while, abscisic acid regulates petal senescence in ethylene-independent systems. Recent research on ethylene-sensitive flowers revealed that the crosstalk of ethylene with sugars and other growth regulators plays a crucial role in modulating senescence by affecting the expression of ethylene-responsive genes. Despite the plethora of postharvest studies conducted so far, considerable miss links still persist in understanding the intricacies of senescence regulating mechanisms, mainly in ethylene-responsive flowers. To this end, it is imperative to critically re-evaluate our current understanding of ethylene-dependent flower senescence to gain intricate inputs regarding the underlying senescence mechanisms, particularly in ornamental families like Ranunculaceae. This constitutes the pivotal gateway toward deciphering the enigmatic complexities governing senescence regulatory mechanisms, thereby forging a path for postharvest researchers to craft pioneering methodologies aimed at accentuating the longevity of commercially significant flowers, thereby yielding substantial economic ramifications."
Authors: Yi Zhang, Yingying Xing, Xinyu Tian, Liuhui Yang, Likai Wang, Zhiyong Guan, Jiafu Jiang, Fadi Chen and Sumei Chen.
Postharvest Biology and Technology (2024)
Highlights: • Sucrose antagonizes SL-induced leaf senescence in chrysanthemum. • Various genes antagonistically regulated by SL and sucrose were revealed by RNA-seq. • CmWRKY6-Like positively regulates leaf senescence in chrysanthemum. • CmWRKY6-Like involves the antagonistic regulation of leaf senescence by SL and sugar.
Abstract: "Strigolactone (SL), a novel plant hormone, plays a vital role in promoting leaf senescence. Sugar, a nutrient source widely used to retain freshness of cut flowers, was recently reported to alleviate SL-induced leaf senescence; however, the underlying molecular mechanisms remain unclear. Leaf senescence during transportation and storage of cut chrysanthemum considerably affects its shelf life and ornamental value. In this study, we found that sucrose antagonizes SL-induced leaf senescence in chrysanthemum. Transcriptional reprogramming analysis revealed a number of differentially expressed genes antagonistically regulated by SL and sucrose, mainly including those related to SL signaling, sugar signaling, ethylene, auxin, jasmonic acid, reactive oxygen species, chlorophyll metabolism pathways, and transcription factors (such as WRKY, NAC, AP2/ERF, and MYB). Virus-based transient silencing of CmWRKY6-Like in chrysanthemum revealed that CmWRKY6-Like positively regulates leaf senescence and involves the antagonistic regulation of leaf senescence by SL and sucrose. This study provides a basis for understanding the molecular mechanisms underlying the antagonistic roles of SL- and sugar-mediated leaf senescence in chrysanthemum."
Authors; Kohji Yamada and Akira Mine.
Science Advances (2024)
One-sentence summary: In plants, the types and amplitudes of defense outputs against bacterial and fungal pathogens depend on cellular sugars.
Abstract: "Pathogen recognition triggers energy-intensive defense systems. Although successful defense should depend on energy availability, how metabolic information is communicated to defense remains unclear. We show that sugar, especially glucose-6-phosphate (G6P), is critical in coordinating defense in Arabidopsis. Under sugar-sufficient conditions, phosphorylation levels of calcium-dependent protein kinase 5 (CPK5) are elevated by G6P-mediated suppression of protein phosphatases, enhancing defense responses before pathogen invasion. Subsequently, recognition of bacterial flagellin activates sugar transporters, leading to increased cellular G6P, which elicits CPK5-independent signaling promoting synthesis of the phytohormone salicylic acid (SA) for antibacterial defense. In contrast, while perception of fungal chitin does not promote sugar influx or SA accumulation, chitin-induced synthesis of the antifungal compound camalexin requires basal sugar influx activity. By monitoring sugar levels, plants determine defense levels and execute appropriate outputs against bacterial and fungal pathogens. Together, our findings provide a comprehensive view of the roles of sugar in defense."
Authors: Moritz Göbel and Franziska Fichtner.
Journal of Plant Physiology (2023)
Abstract: "Plants exhibit enormous plasticity in regulating their architecture to be able to adapt to a constantly changing environment and carry out vital functions such as photosynthesis, anchoring, and nutrient uptake. Phytohormones play a role in regulating these responses, but sugar signalling mechanisms are also crucial. Sucrose is not only an important source of carbon and energy fuelling plant growth, but it also functions as a signalling molecule that influences various developmental processes. Trehalose 6-phosphate (Tre6P), a sucrose-specific signalling metabolite, is emerging as an important regulator in plant metabolism and development. Key players involved in sucrose and Tre6P signalling pathways, including MAX2, SnRK1, bZIP11, and TOR, have been implicated in processes such as flowering, branching, and root growth. We will summarize our current knowledge of how these pathways shape shoot and root architecture and highlight how sucrose and Tre6P signalling are integrated with known signalling networks in shaping plant growth."
Authors: Yundong Yuan, Said Khourchi, Shujia Li, Yanfang Du, and Pierre Delaplace.
Plants (2023)
Abstract: "Shoot branching is a complex and tightly regulated developmental process that is essential for determining plant architecture and crop yields. The outgrowth of tiller buds is a crucial step in shoot branching, and it is influenced by a variety of internal and external cues. This review provides an extensive overview of the genetic, plant hormonal, and environmental factors that regulate shoot branching in several plant species, including rice, Arabidopsis, tomato, and wheat. We especially highlight the central role of TEOSINTE BRANCHED 1 (TB1), a key gene in orchestrating bud outgrowth. In addition, we discuss how the phytohormones cytokinins, strigolactones, and auxin interact to regulate tillering/branching. We also shed light on the involvement of sugar, an integral component of plant development, which can impact bud outgrowth in both trophic and signaling ways. Finally, we emphasize the substantial influence of environmental factors, such as light, temperature, water availability, biotic stresses, and nutrients, on shoot branching. In summary, this review offers a comprehensive evaluation of the multifaced regulatory mechanisms that underpin shoot branching and highlights the adaptable nature of plants to survive and persist in fluctuating environmental conditions."
Authors: Zhenzhen Zhang, Zhaochen Zhong and Yan Xiong.
Molecular Plant (2023)
Abstract: "To ensure survival and promote growth, sessile plants have developed intricate internal signaling networks tailored in diverse cells and organs with both shared and specialized functions that respond to various internal and external cues. A fascinating question arises: how can a plant cell or organ diagnose the spatial and temporal information it is experiencing to know “where I am,” and then is able to make the accurate specific responses to decide “where to go” and “how to go,” despite the absence of neuronal systems found in mammals. Drawing inspiration from recent comprehensive investigations into diverse nutrient signaling pathways in plants, this review focuses on the interactive nutrient signaling networks mediated by various nutrient sensors and transducers. We assess and illustrate examples of how cells and organs exhibit specific responses to changing spatial and temporal information within these interactive plant nutrient networks. In addition, we elucidate the underlying mechanisms by which plants employ posttranslational modification codes to integrate different upstream nutrient signals, thereby conferring response specificities to the signaling hub proteins. Furthermore, we discuss recent breakthrough studies that demonstrate the potential of modulating nutrient sensing and signaling as promising strategies to enhance crop yield, even with reduced fertilizer application."
Authors: Stefania Morales-Herrera, Joris Jourquin, Frederic Coppé, Lorena Lopez-Galvis, Tom De Smet, Alaeddine Safi, Maria Njo, Cara A. Griffiths, John D. Sidda, James S. O. Mccullagh, Xiaochao Xue, Benjamin G. Davis, Johan Van der Eycken, Matthew J. Paul, Patrick Van Dijck and Tom Beeckman.
PNAS (2023)
Significance: Plants differ from animals in having an open growth strategy guaranteeing continuous growth and development after embryogenesis. Insight into the signaling networks that control growth and developmental processes in plants has increased considerably in recent decades showing the involvement of transcriptional networks and plant hormones. The open growth strategy involves the spatiotemporal formation of new organs during the entire life cycle such as new lateral roots (LRs) on the primary root axis. The decision to make a new organ requires the accommodation of energy to the right cells at the right time. Our work uncovers a tissue-specific energy balancing network during the early phase of LR formation that integrates energy with auxin signaling through the pivotal sugar signal, trehalose 6-phosphate.
Abstract: "Plant roots explore the soil for water and nutrients, thereby determining plant fitness and agricultural yield, as well as determining ground substructure, water levels, and global carbon sequestration. The colonization of the soil requires investment of carbon and energy, but how sugar and energy signaling are integrated with root branching is unknown. Here, we show through combined genetic and chemical modulation of signaling pathways that the sugar small-molecule signal, trehalose-6-phosphate (T6P) regulates root branching through master kinases SNF1-related kinase-1 (SnRK1) and Target of Rapamycin (TOR) and with the involvement of the plant hormone auxin. Increase of T6P levels both via genetic targeting in lateral root (LR) founder cells and through light-activated release of the presignaling T6P-precursor reveals that T6P increases root branching through coordinated inhibition of SnRK1 and activation of TOR. Auxin, the master regulator of LR formation, impacts this T6P function by transcriptionally down-regulating the T6P-degrader trehalose phosphate phosphatase B in LR cells. Our results reveal a regulatory energy-balance network for LR formation that links the ‘sugar signal’ T6P to both SnRK1 and TOR downstream of auxin."
Authors: Muhammad Asad Ullah Asad, Xianyue Guan, Lujian Zhou, Zhao Qian, Zhang Yan and Fangmin Cheng.
Plant Science (2023)
Highlights • Metabolic network and regulatory mechanism underlying nitrogen deficiency-induced leaf senescence are comprehensively discussed. • Sugar acts as a key regulator for leaf senescence and root C/N ratio by connecting with hormone signaling and N metabolism. • Nitrogen deficiency-induced leaf senescence was closely associated with BRs-mediated autophagy and circadian clock response.
Abstract: "Nitrogen (N) is a basic building block that plays an essential role in the maintenance of normal plant growth and its metabolic functions through complex regulatory networks. Such the N metabolic network comprises a series of transcription factors (TFs), with the coordinated actions of phytohormone and sugar signaling to sustain cell homeostasis. The fluctuating N concentration in plant tissues alters the sensitivity of several signaling pathways to stressful environments and regulates the senescent-associated changes in cellular structure and metabolic process. Here, we review recent advances in the interaction between N assimilation and carbon metabolism in response to N deficiency and its regulation to the nutrient remobilization from source to sink during leaf senescence. The regulatory networks of N and sugar signaling for N deficiency-induced leaf senescence is further discussed to explain the effects of N deficiency on chloroplast disassembly, reactive oxygen species (ROS) burst, asparagine metabolism, sugar transport, autophagy process, Ca2+ signaling, circadian clock response, brassinazole-resistant 1 (BZRI), and other stress cell signaling. A comprehensive understanding for the metabolic mechanism and regulatory network underlying N deficiency-induced leaf senescence may provide a theoretical guide to optimize the source-sink relationship during grain filling for the achievement of high yield by a selection of crop cultivars with the properly prolonged lifespan of functional leaves and/or by appropriate agronomic managements."
Authors: Shahram Shokrian Hajibehzad, Andrés Romanowski and Ronald Pierik.
Current Biology (2023)
Summary: A new study draws attention to photosynthetically produced sucrose as a major shoot-derived and auxin-dependent regulator of root growth and development in plants.
Excerpts: "In a recent issue of Current Biology, a study by Kircher and Schopfer5 from the University of Freiburg suggests that sucrose, generated by photosynthesis and transported through the phloem to the root, serves as the core component for light-dependent lateral root formation."
"These observations hint at the presence of a signal originating from light and reliant on photoreceptor and/or photosynthesis for regulation of lateral root formation."
"Furthermore, they found that supplementing sucrose to the aerial parts of dark-grown seedlings promoted formation of lateral roots (Figure 1). These findings indicate that sucrose is important for lateral root formation and can initiate lateral root formation even in the absence of other potential light cues."
"The authors proposed that shoot-derived sucrose may stimulate the conversion of tryptophan into auxin within the root. Indeed, sucrose treatment seems to moderately induce abundance at the root tip of the TAA1 enzyme involved in auxin synthesis from tryptophan, suggesting that sucrose may stimulate local auxin production in the root tip, which might in turn promote lateral root formation (Figure 1)."
Authors: Elizabeth A. Dun, Philip B. Brewer, Elizabeth M. J. Gillam and Christine A. Beveridge.
Plant and Cell Physiology (2023)
Abstract: There have been substantial advances in our understanding of many aspects of strigolactone regulation of branching since the discovery of strigolactones as phytohormones (Gomez-Roldan et al., 2008; Umehara et al., 2008). These include further insights into the network of phytohormones and other signals that regulate branching, as well as deep insights into strigolactone biosynthesis, metabolism, transport, perception, and downstream signalling. In this review, we provide an update on recent advances in our understanding of how the strigolactone pathway co-ordinately and dynamically regulates bud outgrowth and pose some important outstanding questions that are yet to be resolved
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