Spermidine Induces Expression of Stress Associated Proteins (SAPs) Genes and Protects Rice Seed from Heat Stress-Induced Damage during Grain-Filling.

Min Chen,Farwa Basit,Temoor Ahmed,Qingshan Mou,Yajing Guan,Xiaobo Zhu,Jianyu An,Yuying Fu,Sheng Zhang,Jin Hu

doi:10.3390/antiox10101544

Abstract

Heat stress during seed maturation significantly reduced seed size and quality. Polyamines, especially spermidine (Spd), were reported to be closely related to seed development and plant heat tolerance. Stress-associated proteins (SAPs) also played a critical role in plant heat resistance, but the relationship between Spd and SAPs in improving rice tolerance to heat stress during grain filling has not been reported. Our results showed that the external spraying Spd (1.5 mM) significantly increased seed germination rate, germination index, vigor index and 1000-grain weight, significantly increased endogenous Spd, spermine (Spm) content and peroxidase activity; significantly reduced MDA content; and greatly alleviated the impact of heat stress on rice seed quality during grain filling stage as compared with high temperature control. OsSAP5 was the most upregulated expression induced by Spd, and may be mainly involved in the Spd-mediated enhancement of high-temperature resistance during rice seed development. Overexpression of OsSAP5 in Arabidopsis enhanced 1000-grain weight and seed heat resistance. Exogenous Spd alleviated the survival rate and seedling length, reduced MDA content, and upregulated the expression levels of SPDS and SPMS in Atsap4 mutant under high temperature during seed germination. In all, exogenous Spd alleviated the heat damage on seed quality during the grain filling stage and seed germination stage by improving endogenous Spd and Spm. OsSAP5, a key gene induced by Spd, might be involved in the rice heat resistance and seed quality in coordination with Spd and Spm.

Highlights

Increasing global temperature has become a significant constraint on global agricultural sustainable development in recent years
When the rice was subjected to high temperature (HT) stress during the early stage of grain filling, the germination percentage (GP), germination index (GI), vigor index (VI), and 1000-grain weight of mature seeds significantly reduced compared with the normal temperature (NT) (Table 1)
The reduction could be significantly alleviated by exogenous Spd spraying, especially the GP and GI reached a similar level as the NT, while the CHA treatment further reduced seed quality as compared with the water spraying under HT (Table 1)

Summary

Introduction

Increasing global temperature has become a significant constraint on global agricultural sustainable development in recent years. Rice (Oryza sativa L.) is one of the most important crops in the world, but it was sensitive to hot temperatures, especially at the heading and filling stages [1,2]. Pollen viability was greatly affected by heat stress, resulting in low seed setting rate and yield decline [3]. The period of grain development was shortened under heat stress, resulting in insufficient grain filling and nutrition accumulation decreased seed size, and low seed quality [4,5]. 1 ◦ C increase in the minimum temperature during the growing season, rice grain yield decreases by 10% [6]. The effect of heat stress during grain filling on offspring germination and development remains to be elucidated

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Results

Discussion

Conclusion