Oryza sativa Transcriptome OsSGT1a gene. Oryza sativa

Heat stress at the flowering stage is an important factor affecting rice grain yield. Although great progress has been made, the cloned genes related to rice heat tolerance at the flowering stage are still very limited. In this study, we characterize the function of heat-induced SGT1 gene, OsSGT1a. Overexpression of OsSGT1a results in decreased heat tolerance whereas RNAi silence or knockout of OsSGT1a results in increased heat tolerance without yield penalty at the flowering stage, as determined by the seed setting rate. OsSGT1a is localized in cytoplasm and mainly expressed in the glume of spikelet. OsSGT1a can interact with the cytoplasmic HSP protein cHSP70-4, and knockout of cHSP70-4 leads to increased heat tolerance. Complementation assay indicates that knockout of cHSP70-4 can restore the weakened heat tolerance of OsSGT1a overexpression plants. Further analysis demonstrates that heat stress can enhance the interaction strength between OsSGT1a and cHSP70-4 in rice. Moreover, our results also show that both OsSGT1a and cHSP70-4 can regulates the expression of a series of PME genes under normal or heat stress conditions at the flowering stage. Together, these observations uncover the pivotal roles of OsSGT1a and cHSP70-4 in regulating rice heat tolerance and provide new target genes for improving heat tolerance at the flowering stage in rice.