Comparative transcriptome analysis of panicle development under heat stress in two rice (Oryza sativa L.) cultivars differing in heat tolerance.

Yaliang Wang,Guohui Hu,Yikai Zhang,Yanhua Chen,Yongtao Cui,Defeng Zhu,Xiaodan Wang,Qiang Zhang,Yuping Zhang,Huizhe Chen,Jing Xiang

doi:10.7717/peerj.7595

Abstract

Heat stress inhibits rice panicle development and reduces the spikelet number per panicle. This study investigated the mechanism involved in heat-induced damage to panicle development and spikelet formation in rice cultivars that differ in heat tolerance. Transcriptome data from developing panicles grown at 40 °C or 32 °C were compared for two rice cultivars: heat-tolerant Huanghuazhan and heat-susceptible IR36. Of the differentially expressed genes (DEGs), 4,070 heat stress-responsive genes were identified, including 1,688 heat-resistant-cultivar-related genes (RHR), 707 heat-susceptible-cultivar-related genes (SHR), and 1,675 common heat stress-responsive genes (CHR). A Gene Ontology (GO) analysis showed that the DEGs in the RHR category were significantly enriched in 54 gene ontology terms, some of which improved heat tolerance, including those in the WRKY, HD-ZIP, ERF, and MADS transcription factor families. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the DEGs in the RHR and SHR categories were enriched in 15 and 11 significant metabolic pathways, respectively. Improved signal transduction capabilities of endogenous hormones under high temperature seemed to promote heat tolerance, while impaired starch and sucrose metabolism under high temperature might have inhibited young panicle development. Our transcriptome analysis provides insights into the different molecular mechanisms of heat stress tolerance in developing rice.

Highlights

Climate change is predicted to increase the average global temperatures by 0.3–4.8 ◦C by the end of the 21st century (Stocher et al, 2013)
The number of differentiated spikelets decreased by 9.6% and 33.2% (P < 0.05) for HHZ and IR36, respectively, and the proportion of degenerated spikelets significantly increased by 32.3% (P < 0.05) and 67.4% (P < 0.05), respectively
The larger reduction in panicle weight in IR36 suggests that high temperature has a greater effect on young panicle development in heat susceptible cultivars (Table 1)

Summary

Introduction

Climate change is predicted to increase the average global temperatures by 0.3–4.8 ◦C by the end of the 21st century (Stocher et al, 2013). High temperatures occur frequently during the rice growing season (Dwivedi et al, 2015; Tao et al, 2013), and cause reductions in the yield and quality in several rice producing regions, including China, India, and Japan (Anand, Kumar & Narayan, 2018; Morita, Wada & Matsue, 2016; Wang et al, 2019). The primary cause of rice yield reductions is a reduction in spikelet fertility due to high temperatures during the flowering period (Espe et al, 2017). As climate change has intensified, extremely high temperatures above 40 ◦C have become more frequent. Such high temperatures inhibit rice panicle development, reduce the spikelet number by 5%–15%, and aggravate rice yield losses (Wang et al, 2017)

Methods

Results

Discussion

Conclusion