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Authors: Jihong Li and Yuan Song.
Plant Science (2024)
Highlights: • The research of plant thermosensor is obviously lagging behind and hence has become an urgent problem to be resolved. • We summarized the recognized and potential plant thermosensors，to describe the multi–level thermal input system in plants. • We reviewed more recent thermosensing mechanisms to facilitate further understanding and studies.
Abstract: "Plants dynamically regulate their genes expression and physiological outputs to adapt to changing temperatures. The underlying molecular mechanisms have been extensively studied in diverse plants and in multiple dimensions. However, the question of exactly how temperature is detected at molecular level to transform the physical information into recognizable intracellular signals remains continues to be one of the undetermined occurrences in plant science. Recent studies have provided the physical and biochemical mechanistic breakthrough of how temperature changes can influence molecular thermodynamically stability, thus changing molecular structures, activities, interaction and signaling transduction. In this review, we focus on the thermosensing mechanisms of recognized and potential plant thermosensors, to describe the multi–level thermal input system in plants. We also consider the attributes of a thermosensor on the basis of thermal-triggered changes in function, structure, and physical parameters. This study thus provides a reference for discovering more plant thermosensors and elucidating plant thermal adaptive mechanisms."
Authors: Hikaru Sato, Junya Mizoi, Kazuo Shinozaki and Kazuko Yamaguchi-Shinozaki.
The Plant Journal (2024)
Significance Statement: In this review, we explain how plants respond to drought, heat, and their combined stress at both physiological and molecular levels. Additionally, we summarize novel resilience mechanisms revealed through natural variations and discuss strategies for developing crops resilient to the increasing dry and hot conditions resulting from climate change.
Abstract: "Global climate change is predicted to result in increased yield losses of agricultural crops caused by environmental conditions. In particular, heat and drought stress are major factors that negatively affect plant development and reproduction, and previous studies have revealed how these stresses induce plant responses at physiological and molecular levels. Here, we provide a comprehensive overview of current knowledge concerning how drought, heat, and combinations of these stress conditions affect the status of plants, including crops, by affecting factors such as stomatal conductance, photosynthetic activity, cellular oxidative conditions, metabolomic profiles, and molecular signaling mechanisms. We further discuss stress-responsive regulatory factors such as transcription factors and signaling factors, which play critical roles in adaptation to both drought and heat stress conditions and potentially function as ‘hubs’ in drought and/or heat stress responses. Additionally, we present recent findings based on forward genetic approaches that reveal natural variations in agricultural crops that play critical roles in agricultural traits under drought and/or heat conditions. Finally, we provide an overview of the application of decades of study results to actual agricultural fields as a strategy to increase drought and/or heat stress tolerance. This review summarizes our current understanding of plant responses to drought, heat, and combinations of these stress conditions."
Authors: Manvi Sharma and Petra Marhava.
Current Opinion in Plant Biology (2023)
Abstract: "Plants have evolved robust adaptive mechanisms to withstand the ever-changing environment. Tightly regulated distribution of the hormone auxin throughout the plant body controls an impressive variety of developmental processes that tailor plant growth and morphology to environmental conditions. The proper flow and directionality of auxin between cells is mainly governed by asymmetrically localized efflux carriers – PINs – ensuring proper coordination of developmental processes in plants. Discerning the molecular players and cellular dynamics involved in the establishment and maintenance of PINs in specific membrane domains, as well as their ability to readjust in response to abiotic stressors is essential for understanding how plants balance adaptability and stability. While much is known about how PINs get polarized, there is still limited knowledge about how abiotic stresses alter PIN polarity by acting on these systems. In this review, we focus on the current understanding of mechanisms involved in (re)establishing and maintaining PIN polarity under abiotic stresses."
Authors: Sheeba John, Federico Apelt, Amit Kumar, Ivan F. Acosta, Dominik Bents, Maria Grazia Annunziata, Franziska Fichtner, Caroline Gutjahr, Bernd Mueller-Roeber and Justyna J. Olas.
Plant Communications (2024)
Abstract: "The shoot apical meristem (SAM) is responsible for overall shoot growth by generating all above-ground structures. Recent research identified that the SAM displays an autonomous heat stress (HS) memory of a previous non-lethal HS event. Considering the importance of the SAM for plant growth it is essential to unlock how its thermomemory is mechanistically controlled. Here, we report that HEAT SHOCK TRANSCRIPTION FACTOR A7b (HSFA7b) plays a crucial role in this process in Arabidopsis, since the absence of functional HSFA7b results in the temporal suppression of the SAM activity after thermopriming. We found that HSFA7b directly regulates ethylene response at the SAM by binding to the promoter of the key ethylene signaling gene ETHYLENE-INSENSITIVE 3 to establish thermotolerance. Moreover, we demonstrated that HSFA7b regulates the expression of ETHYLENE OVERPRODUCER 1 (ETO1) and ETO1-LIKE 1, both of which encode ethylene biosynthesis repressors, thereby ensuring ethylene homeostasis at the SAM. Taken together, these results indicate a crucial and tissue-specific role of HSFA7b in thermomemory at the Arabidopsis SAM."
Authors: Xiaoling Ma, Kangjia Li, Jiajia Cai and David W. Ow.
Plant Science (2023)
Highlights • Constitutive expression of ZmOXS2a in Arabidopsis retards growth but improves heat tolerance. • Deletion of ARR and TZF domains reduces localization to the PBs and restores wild type phenotype. • Constitutive expression of ZmOXS2a in Arabidopsis down-regulates 890 genes and 27% of them contain ARE. • Transgenic lines are more sensitive to ABA but less sensitive to cytokinin.
Abstract: "As plants encounter various environmental stresses, judicial allocation of resources to stress response is crucial for plant fitness. The plant OXS2 (OXIDATIVE STRESS 2) family has been reported to play important roles in growth regulation and stress response. Here, we report that the maize OXS2 family member ZmOXS2a when expressed in Arabidopsis retards growth including delayed flowering, but improves heat tolerance. ZmOXS2a can be found in the cytoplasm, nucleus and PBs/P bodies (mRNA processing bodies), but heat treatment induces higher accumulation in the PBs. Deletion of ARR (arginine rich region) and TZF (tandem zinc finger) domains for high-affinity RNA-binding reduced PBs accumulation of ZmOXS2a; and unlike ZmOXS2a, expression of this deletion mutant gene affected neither Arabidopsis growth nor heat tolerance. This suggests that ZmOXS2a might be involved in RNA degradation, which would also account for the larger amount of down-regulated genes found in ZmOXS2a expressing lines. Furthermore, 240 of 890 down-regulated genes contain ARE (AU-rich elements) in the mRNA 3′UTR that might be potential targets of ZmOXS2a. Expression of ZmOXS2a also disturbs the response to ABA (abscisic acid) and cytokinin, as GO (gene ontology) analysis shows that 50 and 15 DEGs (differentially expressed genes) are enriched in the GO term for ABA and cytokinin responses, respectively. ZmOXS2a expression lines are more sensitive to ABA, but less sensitive to cytokinin. It is likely that ZmOXS2a promotes the degradation of the mRNA of down-regulated genes containing ARE, which consequently perturbs the hormone pathways that affect stress response-related plant growth."
Authors: Aung Htay Naing, Sangcheol Baek, Jova Riza Campol, Hyunhee Kang and Chang Kil Kim.
Plant Physiology and Biochemistry (2023)
Highlights: • Abiotic stress-induced growth inhibition in petunia was linked to ethylene production. • Loss of ACO4 in petunia reduced stress-induced ethylene and ROS. • ACO4 acts as a negative regulator of stress tolerance.
Abstract: "To investigate the role of ethylene (ET) in abiotic stress tolerance in petunia cv. ‘Mirage Rose’, petunia plants in which the ET biosynthesis gene 1-aminocyclopropane-1-carboxylic acid oxidase 4 (ACO4) was knocked out (phaco4 mutants) and wild-type (WT) plants were exposed to heat and drought conditions. Loss of function of ACO4 significantly delayed leaf senescence and chlorosis under heat and drought stress by maintaining the SPAD values and the relative water content, indicating a greater stress tolerance of phaco4 mutants than that of WT plants. This tolerance was related to the lower ET and reactive oxygen species levels in the mutants than in WT plants. Furthermore, the stress-induced expression of genes related to ET signal transduction, antioxidant and proline activities, heat response, and biosynthesis of abscisic acid was higher in the mutants than in WT plants, indicating a greater stress tolerance in the former than in the latter. These results demonstrate the deleterious effects of stress-induced ET on plant growth and provide a better physiological and molecular understanding of the role of stress ET in the abiotic stress response of petunia. Because the loss of function of ACO4 in petunia improved stress tolerance, we suggest that ACO4 plays a vital role in stress-induced leaf senescence and acts as a negative regulator of abiotic stress tolerance."
Authors: Shouguang Huang and Rainer Hedrich.
Current Biology (2023)
Editor's view: Huang and Hedrich demonstrate that Venus flytraps can recognize heat waves and close in the forefront of fires using a trigger-hair-localized thermo-electrical alarm system. Upon calcium-electrical excitation, the traps close, protecting the vulnerable trigger hairs from burning and enabling them to resume capturing prey after the fire has passed.
Highlights: • The trigger hair podium converts thermal energy into a propagating Ca2+ wave • Heat provokes action potentials and Ca2+ waves, which initiate flytrap closure • Flytrap's thermosensor detects critical temperatures and the rise-time velocity • Heat sensor is primed to sense the change rather than absolute temperature
Abstract: "Most plants suffer greatly from heat in general and fire in particular, but some can profit from what is called fire ecology.1 Dionaea muscipula, the Venus flytrap, is one such plant. In its natural habitat in the Green Swamps, Dionaea often faces challenges from excessive growth of grass and evergreen shrubs that overshadow the plant.2 Without natural fire, the Dionaea populations would decline.3 How does Dionaea survive and even thrive after swamp fires? Here, we ask whether flytraps recognize heat waves at the forefront of swamp fires and demonstrate that a heat-sensor-based alarm may provide a fire survival strategy for them. In this study, we show that flytraps become electrically excited and close in response to a heat wave. Over a critical temperature of 38°C, traps fire action potentials (APs), which are interconnected with cytosolic Ca2+ transients. The heat-induced Ca2+-AP has a 3-min refractory period, yet traps still respond to cold, voltage, and glutamate. The heat responses were trap specific, emerging only when the trap became excitable. Upon heat stimulation, the Ca2+ wave originates in the trigger hair podium, indicating that the mechanosensory zone serves as a heat receptor organ. In contrast to the human heat receptor, the flytrap sensor detects temperature change rather than the absolute body temperature. We propose that by sensing the temperature differential, flytraps can recognize the heat of an approaching fire, thus closing before the trigger hairs are burned, while they can continue to catch prey throughout hot summers."
Authors: Hongwei Jing, Edward G. Wilkinson, Katelyn Sageman-Furnas and Lucia C. Strader.
Journal of Experimental Botany (2023)
Abstract: "Plants are exposed to a variety of abiotic stresses; these stresses have profound effects on plant growth, survival, and productivity. Tolerance and adaptation to stress require sophisticated stress sensing, signaling, and various regulatory mechanisms. The plant hormone auxin is a key regulator of plant growth and development, playing pivotal roles in the integration of abiotic stress signals and control of downstream stress responses. In this review, we summarize and discuss recent advances in understanding the intersection of auxin and abiotic stress in plants, with a focus on temperature, salt, and drought stresses. We also explore the auxin roles in stress tolerance and arising opportunities for agricultural applications."
Authors: Megha Sharma, Shivanti Negi, Pankaj Kumar, Dinesh Kumar Srivastava, Mani Kant Choudhary and Mohammad Irfan.
Plan Science (2023)
Highlights: • Heat stress adversely affects fruit quality traits of many crops. • Heat stress regulates ethylene biosynthesis and signaling in plants. • Ethylene also controls the expression of heat shock proteins and heat shock factors. • Many ethylene signaling genes work together with heat shock proteins and factors to regulate fruit ripening against heat stress.
Abstract: "Crop production is significantly influenced by climate, and even minor climate changes can have a substantial impact on crop yields. Rising temperature due to climate change can lead to heat stress (HS) in plants, which not only hinders plant growth and development but also result in significant losses in crop yields. To cope with the different stresses including HS, plants have evolved a variety of adaptive mechanisms. In response to these stresses, phytohormones play a crucial role by generating endogenous signals that regulate the plant’s defensive response. Among these, Ethylene (ET), a key phytohormone, stands out as a major regulator of stress responses in plants and regulates many plant traits, which are critical for crop productivity and nutritional quality. ET is also known as a ripening hormone for decades in climacteric fruit and many studies are available deciphering the function of different ET biosynthesis and signaling components in the ripening process. Recent studies suggest that HS significantly affects fruit quality traits and perturbs fruit ripening by altering the regulation of many ethylene biosynthesis and signaling genes resulting in substantial loss of fruit yield, quality, and postharvest stability. Despite the significant progress in this field in recent years the interplay between ET, ripening, and HS is elusive. In this review, we summarized the recent advances and current understanding of ET in regulating the ripening process under HS and explored their crosstalk at physiological and molecular levels to shed light on intricate relationships"
Authors: Xueting Gu, Fuyan Si, Zhengxiang Feng, Shunjie Li, Di Liang, Pei Yang, Chao Yang, Bin Yan, Jun Tang, Yu Yang, Tai Li, Lin Li, Jinling Zhou, Ji Li, Lili Feng, Ji-Yun Liu, Yuanzhu Yang, Yiwen Deng, Xu Na Wu, Zhigang Zhao, Jianmin Wan, Xiaofeng Cao, Xianwei Song, Zuhua He and Junzhong Liu.
Nature Communications (2023)
Editor's view: Gu et al. report that the OsSGS3-tasiRNA-OsARF3 module plays an important role in coordinating the trade-off between heat tolerance and disease resistance, which positively regulates thermotolerance but negatively modulates immunity in rice.
Abstract: "Recurrent heat stress and pathogen invasion seriously threaten crop production, and abiotic stress often antagonizes biotic stress response against pathogens. However, the molecular mechanisms of trade-offs between thermotolerance and defense remain obscure. Here, we identify a rice thermo-sensitive mutant that displays a defect in floret development under high temperature with a mutation in SUPPRESSOR OF GENE SILENCING 3a (OsSGS3a). OsSGS3a interacts with its homolog OsSGS3b and modulates the biogenesis of trans-acting small interfering RNA (tasiRNA) targeting AUXIN RESPONSE FACTORS (ARFs). We find that OsSGS3a/b positively, while OsARF3a/b and OsARF3la/lb negatively modulate thermotolerance. Moreover, OsSGS3a negatively, while OsARF3a/b and OsARF3la/lb positively regulate disease resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo) and the fungal pathogen Magnaporthe oryzae (M. oryzae). Taken together, our study uncovers a previously unknown trade-off mechanism that regulates distinct immunity and thermotolerance through the OsSGS3-tasiRNA-OsARF3 module, highlighting the regulation of abiotic-biotic stress response trade-off in plants."
Authors: Takuya Furumoto, Shohei Yamaoka, Takayuki Kohchi, Hiroyasu Motose and Taku Takahashi.
bioRxiv (2023)
Abstract: "Thermospermine, a structural isomer of spermine, suppresses auxin-inducible xylem differentiation, whereas spermine is implicated in stress responses in angiosperms. Thermospermine synthase ACAULIS5 (ACL5) is well conserved from algae to land plants, but its physiological function remains elusive in non-vascular plants. Here we focused on MpACL5, a gene in the liverwort Marchantia polymorpha, which rescued the dwarf phenotype of the acl5 mutant of Arabidopsis. In the Mpacl5 mutants generated by genome editing, growth of the vegetative organ, thallus, and the sexual reproductive organ, gametangiophore, was severely retarded. The mutant gametangiophore exhibited remarkable morphological defects such as short stalks, fasciation, and indeterminate growth; it was formed as a fusion of two gametangiophores and a new gametangiophore was often initiated from the old one. Furthermore, Mpacl5 was shown to be hypersensitive to heat and salt stresses. Given the absence of spermine in liverworts including M. polymorpha, these results reveal that thermospermine has a dual primordial function in organ development and stress responses in the basal land plant lineage, the latter of which may have eventually been assigned to spermine during the land plant evolution."
Authors: Xueying Zhang, Linying Li, Yuqing He, Zhuoliang Lang, Yao Zhao, Han Tao, Qingsheng Li and Gaojie Hong.
Plant, Cell & Environment (2023)
Abstract: "High temperatures (HTs) seriously affect the yield and quality of tea. Catechins, derived from the flavonoid pathway, are characteristic compounds that contribute to the flavour of tea leaves. In this study, we first showed that the flavonoid content of tea leaves was significantly reduced under HT conditions via metabolic profiles; and then demonstrated that two transcription factors, CsHSFA1b and CsHSFA2 were activated by HT and negatively regulate flavonoid biosynthesis during HT treatment. Jasmonate (JA), a defensive hormone, plays a key role in plant adaption to environmental stress. However, little has been reported on its involvement in HT response in tea. Herein, we demonstrated that CsHSFA1b and CsHSFA2 activate CsJAZ6 expression through directly binding to heat shock elements in its promoter, and thereby repress the JA pathway. Most secondary metabolites are regulated by JA, including catechin in tea. Our study reported that CsJAZ6 directly interacts with CsEGL3 and CsTTG1 and thereby reduces catechin accumulation. From this, we proposed a CsHSFA-CsJAZ6-mediated HT regulation model of catechin biosynthesis. We also determined that negative regulation of the JA pathway by CsHSFAs and its homologues is conserved in Arabidopsis. These findings broaden the applicability of the regulation of JAZ by HSF transcription factors and further suggest the JA pathway as a valuable candidate for HT-resistant breeding and cultivation."
Authors: Romana Kopecká, Michaela Kameniarová, Martin Černý, Břetislav Brzobohatý and Jan Novák.
International Journal of Molecular Sciences (2023)
Abstract: "The vast majority of agricultural land undergoes abiotic stress that can significantly reduce agricultural yields. Understanding the mechanisms of plant defenses against stresses and putting this knowledge into practice is, therefore, an integral part of sustainable agriculture. In this review, we focus on current findings in plant resistance to four cardinal abiotic stressors—drought, heat, salinity, and low temperatures. Apart from the description of the newly discovered mechanisms of signaling and resistance to abiotic stress, this review also focuses on the importance of primary and secondary metabolites, including carbohydrates, amino acids, phenolics, and phytohormones. A meta-analysis of transcriptomic studies concerning the model plant Arabidopsis demonstrates the long-observed phenomenon that abiotic stressors induce different signals and effects at the level of gene expression, but genes whose regulation is similar under most stressors can still be traced. The analysis further reveals the transcriptional modulation of Golgi-targeted proteins in response to heat stress. Our analysis also highlights several genes that are similarly regulated under all stress conditions. These genes support the central role of phytohormones in the abiotic stress response, and the importance of some of these in plant resistance has not yet been studied. Finally, this review provides information about the response to abiotic stress in major European crop plants—wheat, sugar beet, maize, potatoes, barley, sunflowers, grapes, rapeseed, tomatoes, and apples."
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Authors: Takuya Furumoto, Shohei Yamaoka, Takayuki Kohchi, Hiroyasu Motose and Taku Takahashi.
Plant and Cell Physiology (2024)
Abstract: "Thermospermine suppresses auxin-inducible xylem differentiation, whereas its structural isomer, spermine, is involved in stress responses in angiosperms. The thermospermine synthase, ACAULIS5 (ACL5), is conserved from algae to land plants, but its physiological functions remain elusive in non-vascular plants. Here, we focused on MpACL5, a gene in the liverwort Marchantia polymorpha, that rescued the dwarf phenotype of the acl5 mutant in Arabidopsis. In the Mpacl5 mutants generated by genome editing, severe growth retardation was observed in the vegetative organ, thallus, and the sexual reproductive organ, gametangiophore. The mutant gametangiophores exhibited remarkable morphological defects such as short stalks, fasciation, and indeterminate growth. Two gametangiophores fused together and new gametangiophores were often initiated from the old ones. Furthermore, Mpacl5 showed altered responses to heat and salt stresses. Given the absence of spermine in bryophytes, these results suggest that thermospermine has a dual primordial function in organ development and stress responses in M. polymorpha. The stress response function may have eventually been assigned to spermine during land plant evolution."
Authors: Ming-Che James Liu, Fang-Ling Jessica Yeh, Robert Yvon, Kelly Simpson, Samuel Jordan, James Chambers, Hen-Ming Wu and Alice Y. Cheung.
Cell (2024)
Editor's view: In deciphering the global signaling capacity of FERONIA receptor kinase, Liu, Yeh, et al. discovered an extracellular phase separation process driven by FERONIA peptide ligand RALF-cell wall polysaccharide pectin interaction, which leads to cognate and non-cognate receptor clustering and promiscuous endocytosis as a coping mechanism in response to environmental stressors.
Highlights: • Cell surface pectin-RALF1 phase separation recruits FERONIA-LLG1 into condensates • RALF induces FERONIA-LLG1-dependent promiscuous receptor clustering and endocytosis • RALF1-pectin molecular condensates function as surface sensors for stress signals • FERONIA-LLG1-mediated global endocytosis ensures plant resilience under stress
Abstract: "The FERONIA (FER)-LLG1 co-receptor and its peptide ligand RALF regulate myriad processes for plant growth and survival. Focusing on signal-induced cell surface responses, we discovered that intrinsically disordered RALF triggers clustering and endocytosis of its cognate receptors and FER- and LLG1-dependent endocytosis of non-cognate regulators of diverse processes, thus capable of broadly impacting downstream responses. RALF, however, remains extracellular. We demonstrate that RALF binds the cell wall polysaccharide pectin. They phase separate and recruit FER and LLG1 into pectin-RALF-FER-LLG1 condensates to initiate RALF-triggered cell surface responses. We show further that two frequently encountered environmental challenges, elevated salt and temperature, trigger RALF-pectin phase separation, promiscuous receptor clustering and massive endocytosis, and that this process is crucial for recovery from stress-induced growth attenuation. Our results support that RALF-pectin phase separation mediates an exoskeletal mechanism to broadly activate FER-LLG1-dependent cell surface responses to mediate the global role of FER in plant growth and survival."
Authors: Wenrong Tan, Junhua Chen, Xiaolan Yue, Shuli Chai, Wei Liu, Chenglin Li, Feng Yang, Yongfeng Gao, Lucas Gutiérrez Rodríguez, Víctor Resco de Dios, Dawei Zhang and Yinan Yao.
Science Advances (2023)
Abstract: "During summer, plants often experience increased light inputs and high temperatures, two major environmental factors with contrasting effects on thermomorphological traits. The integration of light and temperature signaling to control thermomorphogenesis in plants is critical for their acclimation in such conditions, but the underlying mechanisms remain largely unclear. We found that heat shock transcription factor 1d (HSFA1d) and its homologs are necessary for plant thermomorphogenesis during the day. In response to warm daytime temperature, HSFA1s markedly accumulate and move into the nucleus where they interact with phytochrome-interacting factor 4 (PIF4) and stabilize PIF4 by interfering with phytochrome B–PIF4 interaction. Moreover, we found that the HSFA1d nuclear localization under warm daytime temperature is mediated by constitutive photomorphogenic 1–repressed GSK3-like kinase BIN2. These results support a regulatory mechanism for thermomorphogenesis in the daytime mediated by the HSFA1s-PIF4 module and uncover HSFA1s as critical regulators integrating light and temperature signaling for a better acclimation of plants to the summer high temperature."
Authors: Juraj Kleman and Radoslava Matusova
Biologia (2023)
Abstract: "The discovery of strigolactones has resulted in a confluence of various research topics like parasitic plants, arbuscular mycorrhizal fungi and phytohormones, which all play a big role in current global agricultural production. Over the past few decades, strigolactone research swiftly gained a spotlight, as to reveal their possible functions within plants and also the surrounding organisms in the rhizosphere. In this review, we explore the discovered functions of strigolactones with the main focus on the chemical structure of strigolactones and how it relates to the various biological responses they cause. We highlight their involvement in plant responses to abiotic stressors, like lack of available nutrients, high salinity, drought, extreme temperatures and presence of potentially toxic elements of environmental importance, while reflecting upon the strigolactone-mediated plant associations with arbuscular mycorrhizal fungi and nodule-forming, N-fixing bacteria. Furthermore, we elaborate on the current state of applied strigolactone research in agriculture and the probable bright future these compounds have in commercial use and what hurdles need to be overcome before they can be fully utilized."
Authors: Yi Kan, Xiao-Rui Mu, Jin Gao, Hong-Xuan Lin and Youshun Lin.
Molecular Plant (2023)
Abstract: "Global warming impacts crop production and threatens food security. Elevated temperatures are sensed by different cell components. Temperature increases are classified as either mild warm temperatures or excessively hot temperatures, and these are perceived by distinct signaling pathways in plants. Warm temperatures induce thermomorphogenesis, while high temperature stress triggers heat acclimation and causes destructive effects on plant growth and development. In this review, we systematically summarize the heat-responsive genetic networks in Arabidopsis and crop plants based on recent studies. In addition, this review highlights the strategies used to improve grain yield under heat stress from a source-sink perspective. We also discuss the remaining issues about the characteristics of thermosensors and the urgency required to explore the basis of acclimation under a multifactorial stress combination."
In: phys.org
Excerpts:"How does the plant protect its vital snap traps and sensory hairs from fire? Biophysicists Professor Rainer Hedrich and Dr. Shouguang Huang from Julius-Maximilians-University (JMU) Würzburg in Bavaria, Germany, have found out: The Venus flytrap uses special heat receptors in the sensory hairs for this purpose, as the researchers report in the journal Current Biology."
"He found that when a local leaf temperature of 37°C was exceeded, the heated area of the trap produced an electrical impulse, an action potential that spread across both halves of the trap. "When the temperature increased further to 55°C, a second action potential was triggered and the trap snapped shut," Shouguang said. But the trap's reaction at 37°C and 55°C only kicked in when temperatures increased abruptly, as in a rapid heat wave. If the temperature rose only slowly, as on hot summer days, the traps did not react."
"Each half of the trap has three sensory hairs that are highly sensitive to touch and generate action potentials. The action potentials are generated at the base of the hairs. There, ion channels that get activated by touch allow calcium to flow into the cells. This calcium signal is the trigger and at the same time an integral part of an action potential. Heat jumps cause the same calcium-dependent electrical events in the sensory hairs as touch."
Authors: Xiang Li, Jianhua Lu, Xuling Zhu, Yanqi Dong, Yanli Liu, Shanshan Chu, Erhui Xiong, Xu Zheng and Yongqing Jiao.
Plant Communications (2023)
Abstract: "Heat stress caused by global warming requires the development of thermotolerant crops to sustain yield. It is necessary to understand the molecular mechanisms underlying heat tolerance in plants. Strigolactones (SLs) are a class of carotenoid-derived phytohormones that regulate plant development and responses to abiotic or biotic stresses. Although SL biosynthesis and signaling processes are well established, genes directly regulating SL biosynthesis have rarely been reported. Here, we report that the MYB-like transcription factor AtMYBS1/AtMYBL, whose gene expression is repressed by heat stress, functions as a negative regulator of heat tolerance by directly inhibiting SL biosynthesis in Arabidopsis. Overexpression of AtMYBS1 led to heat hypersensitivity, while atmybs1 mutants displayed increased heat tolerance. The expression of MAX1, a critical enzyme in SL biosynthesis, was induced by heat stress and downregulated in AtMYBS1 overexpression (OE) plants but was upregulated in atmybs1 mutants. Overexpression of MAX1 in the AtMYBS1 OE background reversed the heat hypersensitivity of AtMYBS1 OE plants. Loss of function of MAX1 in the atmyb1 background reversed the heat-tolerant phenotypes of atmyb1 mutants. Yeast one-hybrid, ChIP‒qPCR, and transgenic analyses demonstrated that AtMYBS1 directly represses MAX1 expression through the MYB-binding site in the MAX1 promoter in vivo. The atmybs1d14 double mutant, similar to d14 mutants, exhibited hypersensitivity to heat stress, indicating the necessary role of SL signaling in AtMYBS1-regulated heat tolerance. Our findings provide new insights into the regulatory network of SL biosynthesis, facilitating the breeding of heat-tolerant crops to improve crop production in a warming world."
Authors: Richard V. Espley and Laura Jaakola.
Plant, Cell & Environment (2023)
Abstract: "For many fruit crops, the colour of the fruit outwardly defines its eating quality. Fruit pigments provide reproductive advantage for the plant as well as providing protection against unfavourable environmental conditions and pathogens. For consumers these colours are considered attractive and provide many of the dietary benefits derived from fruits. In the majority of species, the main pigments are either carotenoids and/or anthocyanins. They are produced in the fruit as part of the ripening process, orchestrated by phytohormones and an ensuing transcriptional cascade, culminating in pigment biosynthesis. Whilst this is a controlled developmental process, the production of pigments is also attuned to environmental conditions such as light quantity and quality, availability of water and ambient temperature. If these factors intensify to stress levels, fruit tissues respond by increasing (or ceasing) pigment production. In many cases, if the stress is not severe, this can have a positive outcome for fruit quality. Here, we focus on the principal environmental factors (light, temperature and water) that can influence fruit colour."
Authors: Robert Säbel, Alejandro Brand, Nick Bergau, Gerd Balcke, Frank Syrowatka, Mandy Püffeld-Raorane, Bettina Hause and Alain F Tissier.
bioRxiv (2023)
Abstract: "Cultivated tomato (Solanum lycopersicum) and related wild species develop several types of trichomes, both glandular and non-glandular, on their aerial parts. Among these, type-IV trichomes are responsible for the synthesis and secretion of acylsugars, which act as defense compounds against herbivores. In contrast to related wild species such as S. pennellii, type-IV trichomes are present only in the juvenile stages of cultivated tomato plants and absent in later stages of development. By submitting tomato plants to high temperatures during the day (37 °C), we observe that non-glandular type-V trichomes are replaced by type-IV trichomes. This is accompanied by a massive increase in acylsugar production. On the other hand, heat treatment does not affect type VI-trichomes, which produce mono- and sesquiterpenes, but the production of monoterpenes is increased while that of sesquiterpenes is suppressed. Furthermore, tomato jai1 mutants deficient in jasmonate (JA) perception do not exhibit this developmental switch from type-V to type-IV trichomes. The implication of JA signaling in this process was further supported by an increase in JA-isoleucine and in the expression of genes involved in JA-signalling within hours of heat stress application. These results establish a unique system to study how environmental factors affect developmental fate decisions in plants while opening opportunities to understand mechanisms controlling type-IV trichome initiation and development."
Authors: Zhirui Yang, Yibo Cao, Yiting Shi, Feng Qin, Caifu Jiang and Shuhua Yang.
Molecular Plant (2023)
Abstract: "Global climate change exacerbates the effects of environmental stressors, such as drought, flooding, extreme temperatures, salinity and alkalinity, on crop growth and grain yield, threatening the sustainability of the food supply. Maize (Zea mays) is one of the most widely cultivated crops and the most abundant grain crop in production worldwide. However, maize yield stability is highly dependent on environmental conditions. Recently, great progress has been achieved in understanding the molecular mechanisms underlying maize responses to environmental stresses and developing stress-resilient varieties through the rapid advancement of high-throughput sequencing technologies, multi-omics analytic platforms and automated phenotyping facilities. In this review, we summarize recent advances in dissecting the genetic components contributing to maize abiotic stress tolerance through diverse genetic strategies. In addition, we discuss the future challenges and opportunities for developing climate-resilient maize varieties".
Authors: Rahul Michael, Shagun Bali, Ritu Godara and Vivek Dogra.
Trends in Plant Science (2023)
Abstract: "Seed thermoinhibition protects emerging seedlings from thermodamage by preventing seed germination at elevated temperatures. It had remained unknown how a seed fine-tunes its germination in response to temperature. Recently, Piskurewicz et al. demonstrated that endosperm phyB senses increased temperature, thereby facilitating PIF3-mediated abscisic acid (ABA) accumulation to inhibit germination and embryo elongation."
Authors: Jianyan Huang, Xiaobo Zhao, Marco Bürger, Joanne Chory and Xinchao Wang.
Trends in Plant Science (2023)
Highlights: As a major environmental factor impacting the seasonal growth and geographical distribution of plants, temperature change significantly affects crop quality and productivity. Ethylene is a gaseous hormone with an important role in plant growth, development, and multiple stress responses, including heat and cold. Temperature stress affects ethylene biosynthesis and signaling pathways, with APETALA2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF) transcription factors being the main node of ethylene-mediated temperature stress response. Crosstalk among different phytohormones also alters and regulates the expression of temperature stress-responsive genes.
Abstract: "Temperature influences the seasonal growth and geographical distribution of plants. Heat or cold stress occur when temperatures exceed or fall below the physiological optimum ranges, resulting in detrimental and irreversible damage to plant growth, development, and yield. Ethylene is a gaseous phytohormone with an important role in plant development and multiple stress responses. Recent studies have shown that, in many plant species, both heat and cold stress affect ethylene biosynthesis and signaling pathways. In this review, we summarize recent advances in understanding the role of ethylene in plant temperature stress responses and its crosstalk with other phytohormones. We also discuss potential strategies and knowledge gaps that need to be adopted and filled to develop temperature stress-tolerant crops by optimizing ethylene response."
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