TY - JOUR T1 - A Heat Stress Responsive NAC Transcription Factor Heterodimer Plays Key Roles in Rice Caryopsis Filling JF - bioRxiv DO - 10.1101/2020.02.08.939728 SP - 2020.02.08.939728 AU - Ye Ren AU - Zhouquan Huang AU - Hao Jiang AU - Zhuo Wang AU - Fengsheng Wu AU - Yufei Xiong AU - Jialing Yao Y1 - 2020/01/01 UR - http://biorxiv.org/content/early/2020/02/10/2020.02.08.939728.abstract N2 - High temperature usually leads to the failure of grain filling during caryopsis development, resulting in the loss of yield, however the mechanism is not yet well elucidated. Here, we report that two rice caryopsis-specific NAM/ATAF/CUC domain transcription factors, ONAC127 and ONAC129, respond to heat stress and are involved in the caryopsis filling process. ONAC127 and ONAC129 are dominantly expressed in pericarp during grain filling and can form a heterodimer. To investigate the functions of these two ONACs, we obtained CRISPR/cas9 induced mutants and overexpression lines of them. Interestingly, we found that both knock-out and overexpression plants showed incompletely filling and shrunken phenotype of caryopses, which became more severe under heat stress. The shrunken caryopses of these transgenic lines are usually with ectopic accumulation of starch in the pericarp. Transcriptome analyses revealed that ONAC127 and ONAC129 mainly regulate stimulus response, cell wall construction and nutrient transport etc. ChIP-seq analyses identified the direct targets of ONAC127 and ONAC129 in developing caryopses, including monosaccharide transporter OsMST6, sugar transporter OsSWEET4, calmodulin-like protein OsMSR2 and Ethylene-Response AP2/ERF Factor OsEATB. The result suggested that ONAC127 and ONAC129 might regulate the caryopsis filling through sugar transportation and abiotic stress responses. Overall, this study demonstrates the transcriptional regulatory networks involving ONAC127 and ONAC129, which coordinates multiple pathways to modulate caryopsis development and heat stress response at rice filling stage. ER -