Identification of plant hormones and candidate hub genes regulating flag leaf senescence in wheat response to water deficit stress at the grain‐filling stage

Tolerance to water deficit in relation to activities of sucrose-to- starch metabolizing enzymes and starch accumulation was studied in the grains of contrasting wheat (Triticum aestivum L.) genotypes (WH1021 and WH1080; tolerant) and (WH711 and HD2687; susceptible) under late planting conditions. The activities of starch metabolizing enzymes i.e. sucrose synthase (SuSase), ADP-glucose pyrophosphorylase (AGPase), soluble starch synthase (SSS) and starch branching enzymes (SBE) were substantially enhanced by water deficit in all genotypes at early to mid-grain filling stage showing peaks at 14 to 21 days after anthesis (DAA); while decreased significantly at mid-late grain filling stage with maximum decline at 35 DAA. Activities of all the enzymes under study showed maximum decline in activity (28.4–60%) in susceptible genotype WH711; whereas WH1021 proved to be most tolerant one with minimum decline in enzyme activity (14.9–32.8%). Starch content was also markedly reduced (21%) in WH711 due to drought while WH1021 reported 12% decline corresponding well with enzyme activity. A faster pre-mature cessation of starch deposition occurred in susceptible wheat genotypes compared to tolerant ones. A significant and positive correlation of the enzyme activities with starch accumulation (r = 0.491–0.555 at P0.05 for SuSase, AGPase, SSS and r = 0.638 at P0.01 for SBE) under well watered conditions indicated that enhancing the activities of the enzymes would lead to increase in starch accumulation and thus faster grain filling. Genotype WH1021 proved to be most efficient based on comparatively higher enzyme activity and least yield penalty under late planting conditions combined with water scarcity.

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Physiological and Transcriptome Analyses of Early Leaf Senescence for ospls1 Mutant Rice (Oryza sativa L.) during the Grain-Filling Stage

International Journal of Molecular Sciences ◽

10.3390/ijms20051098 ◽

2019 ◽

Vol 20 (5) ◽

pp. 1098 ◽

Cited By ~ 8

Author(s):

Zhaowei Li ◽

Xinfeng Pan ◽

Xiaodong Guo ◽

Kai Fan ◽

Wenxiong Lin

Keyword(s):

Oryza Sativa ◽

Signaling Pathways ◽

Leaf Senescence ◽

Grain Filling ◽

Differentially Expressed ◽

Hormone Signaling ◽

Rna Seq ◽

Filling Stage ◽

Grain Filling Stage ◽

Early Leaf Senescence

Early leaf senescence is an important agronomic trait that affects crop yield and quality. To understand the molecular mechanism of early leaf senescence, Oryza sativa premature leaf senescence 1 (ospls1) mutant rice with a deletion of OsVHA-A and its wild type were employed in this study. The genotype-dependent differences in photosynthetic indexes, senescence-related physiological parameters, and yield characters were investigated during the grain-filling stage. Moreover, RNA sequencing (RNA-seq) was performed to determine the genotype differences in transcriptome during the grain-filling stage. Results showed that the ospls1 mutant underwent significant decreases in the maximal quantum yield of photosystem II (PSII) photochemistry (Fv/Fm), net photosynthesis rate (Pn), and soluble sugar and protein, followed by the decreases in OsVHA-A transcript and vacuolar H+-ATPase activity. Finally, yield traits were severely suppressed in the ospls1 mutant. RNA-seq results showed that 4827 differentially expressed genes (DEGs) were identified in ospls1 mutant between 0 day and 14 days, and the pathways of biosynthesis of secondary metabolites, carbon fixation in photosynthetic organisms, and photosynthesis were downregulated in the senescing leaves of ospls1 mutant during the grain-filling stage. In addition, 81 differentially expressed TFs were identified to be involved in leaf senescence. Eleven DEGs related to hormone signaling pathways were significantly enriched in auxin, cytokinins, brassinosteroids, and abscisic acid pathways, indicating that hormone signaling pathways participated in leaf senescence. Some antioxidative and carbohydrate metabolism-related genes were detected to be differentially expressed in the senescing leaves of ospls1 mutant, suggesting that these genes probably play response and regulatory roles in leaf senescence.

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Scheduling of nitrogen fertilizer topdressing during panicle differentiation to improve grain yield of rice with a long growth duration

Scientific Reports ◽

10.1038/s41598-020-71983-y ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Yang Liu ◽

Xinguang Zhu ◽

Xiaoe He ◽

Chao Li ◽

Tiangen Chang ◽

...

Keyword(s):

Grain Yield ◽

Nitrogen Fertilizer ◽

Flag Leaf ◽

Grain Filling ◽

Rice Cultivars ◽

Growth Duration ◽

Filling Stage ◽

Initial Stage ◽

Grain Filling Stage ◽

Leaf Extension

Abstract Topdressing at panicle differentiation (PF) according to soil fertility and regularity of rice nutrient absorption is an important agronomic practice used in cultivation of rice cultivars with a long growth duration. We studied the impacts of timing of nitrogen fertilizer application during PF on photosynthesis and yield-related agronomic traits in ‘Y-Liang-You 900’ and ‘Y-Liang-You 6’, which are representative rice cultivars with a long growth duration. Data for two years showed that timing of topdressing application during PF affected panicles per unit area, percentage grain set, spikelets per panicle, and leaf photosynthetic traits during the grain-filling period. Topdressing at the initial stage of flag-leaf extension resulted in higher grain yield (typically by 10.55–19.95%) than in plants without topdressing. Grain yield was significantly correlated with flag leaf photosynthetic rate and leaf SPAD value (r = 0.5640 and r = 0.5589, respectively; p < 0.01) at an advanced grain-filling stage (30 days after heading). Surprisingly, grain yield was not correlated with carbohydrate remobilization from the stem and sheath. For rice cultivars with a long growth duration, nitrogen-fertilizer topdressing must be applied at the initial stage of flag-leaf extension to delay leaf senescence during the grain-filling stage and realize the enhanced yield potential.

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