Rice EARLY SENESCENCE 2, encoding an inositol polyphosphate kinase, is involved in leaf senescence

Shenglong Yang,Guonan Fang,Chaolei Liu,Shilin Ding,Noushin Jaha,Yu Zhang,Jiayu Wang,Zhengjin Xu,Peng Hu,Qian Qian,Banpu Ruan,Hongzhen Jiang,Anpeng Zhang,Zhenyu Gao

doi:10.1186/s12870-020-02610-1

Abstract

BackgroundEarly leaf senescence influences yield and yield quality by affecting plant growth and development. A series of leaf senescence-associated molecular mechanisms have been reported in rice. However, the complex genetic regulatory networks that control leaf senescence need to be elucidated.ResultsIn this study, an early senescence 2 (es2) mutant was obtained from ethyl methanesulfonate mutagenesis (EMS)-induced mutational library for the Japonica rice cultivar Wuyugeng 7 (WYG7). Leaves of es2 showed early senescence at the seedling stage and became severe at the tillering stage. The contents of reactive oxygen species (ROS) significantly increased, while chlorophyll content, photosynthetic rate, catalase (CAT) activity significantly decreased in the es2 mutant. Moreover, genes which related to senescence, ROS and chlorophyll degradation were up-regulated, while those associated with photosynthesis and chlorophyll synthesis were down-regulated in es2 mutant compared to WYG7. The ES2 gene, which encodes an inositol polyphosphate kinase (OsIPK2), was fine mapped to a 116.73-kb region on chromosome 2. DNA sequencing of ES2 in the mutant revealed a missense mutation, ES2 was localized to nucleus and plasma membrane of cells, and expressed in various tissues of rice. Complementation test and overexpression experiment confirmed that ES2 completely restored the normal phenotype, with chlorophyll contents and photosynthetic rate increased comparable with the wild type. These results reveal the new role of OsIPK2 in regulating leaf senescence in rice and therefore will provide additional genetic evidence on the molecular mechanisms controlling early leaf senescence.ConclusionsThe ES2 gene, encoding an inositol polyphosphate kinase localized in the nucleus and plasma membrane of cells, is essential for leaf senescence in rice. Further study of ES2 will facilitate the dissection of the genetic mechanisms underlying early leaf senescence and plant growth.

Highlights

Leaf senescence influences yield and yield quality by affecting plant growth and development
ES2 was localized to nucleus and plasma membrane and expressed in various tissues of rice To determine subcellular localization of the ES2 protein, the p35S::ES2::GFP vector was transferred into rice protoplasts and tobacco (N. benthamiana), respectively, with the p35S:: GFP empty vector as control (Additional file 8: Figure S4a-c, g-i)
The quantitative real-time PCR (qRT-PCR) results showed that the expression level of OsIPK2 in es2 was significantly up-regulated at seedling stage, while down-regulated at tillering and heading stage compared with Wuyugeng 7 (WYG7) (Additional file 11: Figure S7)

Summary

Introduction

Leaf senescence influences yield and yield quality by affecting plant growth and development. Leaf cells undergo drastic physiological and metabolic changes in an orderly manner, such as chlorophyll degradation, oxidation and hydrolysis of proteins, lipids and nucleic acids [1]. These hydrolyzed metabolites remobilize to new bud, stem or root in perennial plants or to seed in annual plants [2]. In some hybrid rice varieties, early senescence leads to impaired leaf function and reduced accumulation of photosynthetic products, which impact rice yield [7, 8]. It is important to understand the mechanism underlying early leaf senescence for rice breeding

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Conclusion