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Authors: Mei-Qing Xing, Su-Hui Chen, Xiao-Fan Zhang and Hong-Wei Xue.
Plant Biotechnology Journal (2023)
Except: "A preliminary agar plate assay showed a much higher α-amylase activity of OsGA2ox9-Cas9 seeds, compared to ZH11 (Figure 1g, left). Consistently, transcription analysis confirmed the significantly increased expression of α-amylase encoding genes OsAmy (1B, 1C, 3A, 3B, 3C and 3E) in OsGA2ox9-Cas9 seeds (Figure 1g, right). The promoter activities of OsAmy1C, 3A, 3B and 3E were detected in the endosperm adjacent to scutellum (Nakata et al., 2017), which closely related to OsGA2ox9 expression, suggesting that OsGA2ox9 might regulate the transcription of α-amylase encoding genes through GA signalling. As α-amylases hydrolyse starch granules into soluble sugars, measurement indeed showed the increased contents of glucose and sucrose in OsGA2ox9-Cas9 seeds (Figure 1h). Sugar of rice endosperm is sufficient to suppress the expression of ABA signalling genes and result in PHS (Du et al., 2018), suggesting that sugar may suppress seed dormancy through modulating ABA signalling. Indeed, developing OsGA2ox9-Cas9 panicles showed reduced dormancy (higher germination) under ABA (Figure 1i), and transcriptions of OsABI3 and OsABI5, key positive regulators controlling seed dormancy, were significantly decreased (Figure 1j), indicating that GA-promoted starch hydrolysis led to reduced ABA signalling."
Authors: Da Cao, Tinashe Chabikwa, Francois Barbier, Elizabeth A. Dun, Franziska Fichtner, Lili Dong, Stephanie C. Kerr and Christine A. Beveridge.
Plant Physiology (2023)
Short summary: Sugars and cytokinin initiate bud release independently of auxin and suppress inhibition by SL. Afterward, auxin in buds regulates gibberellin to promote sustained bud growth.
Abstract: "The inhibition of shoot branching by the growing shoot tip of plants, termed apical dominance, was originally thought to be mediated by auxin. Recently the importance of the shoot tip sink strength during apical dominance has re-emerged with recent studies highlighting roles for sugars in promoting branching. This raises many unanswered questions on the relative roles of auxin and sugars in apical dominance. Here we show that auxin depletion after decapitation is not always the initial trigger of rapid cytokinin increases in buds that are instead correlated with enhanced sugars. Auxin may also act through strigolactones which have been shown to suppress branching after decapitation, but here we show that strigolactones do not have a significant effect on initial bud outgrowth after decapitation. We report here that when sucrose or cytokinin is abundant, strigolactones are less inhibitory during the bud release stage compared to during later stages and that strigolactone treatment rapidly inhibits cytokinin accumulation in pea (Pisum sativum) axillary buds of intact plants. After initial bud release, we find an important role of gibberellin in promoting sustained bud growth downstream of auxin. We are therefore able to suggest a model of apical dominance that integrates auxin, sucrose, strigolactones, cytokinins and gibberellins and describes differences in signalling across stages of bud release to sustained growth."
Authors: Wenqiang Pan, Jiahui Liang, Juanjuan Sui, Jingru Li, Chang Liu, Yin Xin, Yanmin Zhang, Shaokun Wang, Yajie Zhao, Jie Zhang, Mingfang Yi, Sonia Gazzarrini and Jian Wu.
Genes (2021)
Abstract: "Bud dormancy is an evolved trait that confers adaptation to harsh environments, and affects flower differentiation, crop yield and vegetative growth in perennials. ABA is a stress hormone and a major regulator of dormancy. Although the physiology of bud dormancy is complex, several advancements have been achieved in this field recently by using genetics, omics and bioinformatics methods. Here, we review the current knowledge on the role of ABA and environmental signals, as well as the interplay of other hormones and sucrose, in the regulation of this process. We also discuss emerging potential mechanisms in this physiological process, including epigenetic regulation."
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Authors: Raz Danieli, Shmuel Assouline, Bolaji Babajide Salam, Ondřej Vrobel, Paula Teper-Bamnolker, Eduard Belausov, David Granot, Petr Tarkowski and Dani Eshel.
Plant, Cell & Environment (2023)
Abstract: "Endodormancy (ED) is a crucial stage in the life cycle of many perennial plants. ED release requires accumulating a certain amount of cold exposure, measured as chilling units. However, the mechanism governing the effect of chilling on ED duration is poorly understood. We used the potato tuber model to investigate the response to chilling as associated with ED release. We measured the accumulation of specific sugars during and after chilling, defined as sugar units. We discovered that ED duration correlated better with sugar units accumulation than chilling units. A logistic function was developed based on sugar units measurements to predict ED duration. Knockout or overexpression of the vacuolar invertase gene (StVInv) unexpectedly modified sugar units levels and extended or shortened ED, respectively. Silencing the energy sensor SNF1-related protein kinase 1, induced higher sugar units accumulation and shorter ED. Sugar units accumulation induced by chilling or transgenic lines reduced plasmodesmal (PD) closure in the dormant bud meristem. Chilling or knockout of abscisic acid (ABA) 8′-hydroxylase induced ABA accumulation, in parallel to sweetening, and antagonistically promoted PD closure. Our results suggest that chilling induce sugar units and ABA accumulation, resulting in antagonistic signals for symplastic connection of the dormant bud."
Authors: Firdous Rasool Sheikh, Joel Jose-Santhi, Diksha Kalia, Kulwinder Singh and Rajesh Kumar Singh.
Industrial Crops and Products (2022)
Highlights: • The role of sugars in controlling dormancy and sprouting has been discussed in this review.. • Sugars, type and metabolism, differ in different storage organs in geophytes. • External and internal factors tune sugar metabolism differently during dormancy. • A similar yet divergent mechanism is involved in above/below ground organ dormancy-sprouting regulation.
Abstract: "Geophytes develop underground storage organs, which help them to survive extreme environments. Besides energy resources for plants and humans, they are widely used for vegetative propagation. Naturally, these storage organs are sink tissues during the active growth cycle of the plant, but they turn into a source during vegetative propagation. Synchronized dormancy and sprouting with the environment are crucial for plant fitness and maximum yield. The active metabolic status of an underground vegetative organ determines its developmental fate. Sugars are the main components of storage organs; thus, their dynamics play an important role in controlling the dormancy-activity cycle of geophytes. Dormant buds require carbon sources (sugar) to promote growth, and the plant adjusts sugar metabolism between storage and soluble sugars to maintain dormancy and sprouting. In recent years, sugars and their derivatives, besides energy molecules, have also been considered signaling molecules involved in several plant developmental processes, including vegetative dormancy and growth. This review discusses current knowledge on the role of sugars in regulating and controlling dormancy and sprouting in geophytes. It’s regulation by external environmental factors, hormonal regulation and cross-talk. It also outlines how similar or different the regulatory mechanism controlling geophyte dormancy and sprouting is, compared to seed dormancy and germination and seasonal/annual growth in perennials that undergo dormancy-activity cycles.
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