Analysis of the transcriptome and heat-shock protein (HSP) family expression in the spikelets of hulless oat (Avena sativa L.) under heat stress

Oat is an economically important cereal crop with a distinct nutritional profile, including β-glucan and avenin seed storage proteins. Despite its importance, genomic investigations of oat have been delayed due to its large and complex genome. However, the reference genome of oat has recently been published. Therefore, many studies, such as those involving transcriptome analysis and genome-wide gene identification, have been conducted and their results made available. Heat stress can seriously harm plant growth and development, and its impact is worsening due to climate change. Heat shock protein is one of the most well-known proteins that protect plants from diverse biotic and abiotic stressors, including high temperatures. However, the response of oat genes to high temperatures and the HSPs in the oat genome have not yet been investigated. In this study, we performed RNA-seq analysis on oat spikelets from plants grown at high temperatures. We found that glutathione and flavonoid pathways were upregulated, whereas DNA replication and fatty acid elongation were downregulated under heat stress. When we observed the expression of seed component genes at high temperatures, we found that cellulose synthase genes showed diverse expression patterns, whereas avenin genes were severely downregulated. Furthermore, we identified and localized a total of 823 HSP gene families in the oat genome. Their gene expressions at diverse temperatures were also observed, which could help identify HSPs regarding heat response. Our findings will be helpful in future investigations of the complex mechanisms that confer heat tolerance in oat.