Spermidine Enhanced Free Polyamine Levels and Expression of Polyamine Biosynthesis Enzyme Gene in Rice Spikelets under Heat Tolerance before Heading

Rong Zhou,Xiuru Zhu,Jianchang Yang,Moxian Chen,Qijuan Hu,Qiong Pu,Guixiang Zhou,Lijun Liu,Cong Gao,Jianhua Zhang,Zhiqing Wang,Yunying Cao

doi:10.1038/s41598-020-64978-2

Abstract

High temperatures (HT) before heading strongly inhibit the development of spikelets in rice. Spermidine (Spd) can improve rice’s resistance to HT stress; however, the mechanism underlying this effect has not been elucidated. This study investigated several parameters, including yield, superoxide anion (O2.-), protective enzyme activities, and polyamine content, in a heat-sensitive genotype, Shuanggui 1. The yield and yield components decreased dramatically when subjected to HT stress, while this reduction could be partially recovered by exogenous Spd. Spd also slowed the generation rate of O2.- and increased protective enzyme, superoxide dismutase (SOD) and catalase (CAT) activities both under normal and high temperatures, which suggested that Spd may participate in the antioxidant system. Furthermore, genes involved in polyamine synthesis were analyzed. The results show that HT before heading significantly increased the expression of arginine decarboxylase OsADC1, Spd synthase OsSPDS1 and OsSPDS3 and had little effect on the expression of the S-adenosylmethionine decarboxylase OsSAMDC2 and ornithine decarboxylase OsODC1. In addition, exogenous Spd considerably reduced the expression of OsSAMDC2, OsSPDS1 and OsSPDS3 under HT but not the expression of OsADC1. The above mentioned results indicate that the exogenous Spd could help young rice spikelets to resist HT stress by reducing the expression of OsSAMDC2, OsSPDS1 and OsSPDS3, resulting in higher levels of endogenous Spd and Spm, which were also positively correlated with yield. In conclusion, the adverse effect of HT stress on young spikelets seems to be alleviated by increasing the amounts of Spd and Spm, which provides guidance for adaptation to heat stress during rice production.

Highlights

Rice (Oryza sativa L.) is one of the most important staple food crops and feeds approximately 65% of the population in China[5,6]
Biosynthesis of Put, either directly from ornithine or indirectly from arginine via agmatine, is catalyzed by ornithine decarboxylase (ODC) and arginine decarboxylase (ADC); aminopropyl groups are indicated by decarboxylated S-adenosylmethionine (SAM), which is produced from SAM by S-adenosylmethionine decarboxylase (SAMDC); the addition of aminopropyl groups transfer Put into Spd and Spm, which is catalyzed via Spd synthase (SPDS) and Spm synthase (SPMS), respectively
We investigated the polyamine content and expression levels of genes encoding enzymes involved in polyamine biosynthesis in a heat-sensitive genotype, Shuanggui 1, under High temperatures (HT) stress before heading and explored the possible correlations between spikelet sterility, polyamine content, gene expression level and heat sensitivity of the two cultivars by application of exogenous substances

Summary

Introduction

Rice (Oryza sativa L.) is one of the most important staple food crops and feeds approximately 65% of the population in China[5,6]. Activity and/or the transcriptional level of some key enzymes involved in polyamine biosynthesis could be induced by abiotic stress. Free polyamine and gene expression levels of encoding polyamine biosynthesis enzymes were measured in rice seedling leaves under salt stress[21]. The transcript levels of ADC, ODC, SPMS and SAMDC in spikelets under heat stress before heading were not determined in rice. There is little information about the relationship between internal polyamine accumulation and spikelet sterility before heading in rice under heat stress. We investigated the polyamine content and expression levels of genes encoding enzymes involved in polyamine biosynthesis in a heat-sensitive genotype, Shuanggui 1, under HT stress before heading and explored the possible correlations between spikelet sterility, polyamine content, gene expression level and heat sensitivity of the two cultivars by application of exogenous substances

Methods

Results

Conclusion