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

Zhaowei Li,Kai Fan,Xiaodong Guo,Xinfeng Pan,Wenxiong Lin

doi:10.3390/ijms20051098

Zhaowei Li, Kai Fan + Show 3 more

Open Access

https://doi.org/10.3390/ijms20051098

Copy DOI

Abstract

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.

Highlights

Senescence is the final stage of leaf development and corresponds to the programmed degradation of cells, tissues, organs, and the entire organism [1]
Our results showed that the ospls1 mutant rice underwent early leaf senescence in comparison with its wild type during the grain-filling stage
Physiological and agronomic analysis showed that the ospls1 mutant displayed significant decreases in soluble sugar and protein, photosynthesis rate (Pn), and yield traits, accompanied by decreases in OsVHA-A transcript and V-H+-ATPase activity

Summary

Introduction

Senescence is the final stage of leaf development and corresponds to the programmed degradation of cells, tissues, organs, and the entire organism [1]. 81 DEGs between 0 day and 14 days in these two genotypes were identified and characterized as TFs (Supplementary Table S4) They were clustered into 13 gene families: Homeobox-ZIP, WRKY, AUX-IAA, NAC, HMG, HAP3, PCF, SPL, PHD-finger, MADS-box, DREB, Zinc-finger, and MYB (Figure 5). The majority of Homeobox-ZIP genes had significantly high transcript abundance in the leaves of the two genotypes, such as homeobox-leucine zipper protein HOX1, HOX4, HOX5, HOX7, HOX10, HOX11, HOX15, HOX16, HOX20, HOX22, HOX27, and HOX32 (Figure 6). Another significantly represented family was WRKY, around 23.6% of the TFs (Figure 5). The WRKY TFs 24, 39, 44, 53, 67, 70, 71, 72, 74, and 76 showed steadily high transcript abundance in the two genotypes, whereas WRKY TFs 42, 49, and 70 were among those differentially expressed in the ospls mutant and wild type (Figure 6)

Methods

Results

Discussion

Conclusion