The role of rice SOG1 and SOG1-like in DNA damage response

Higher plants are constantly exposed to environmental stresses, and therefore complicated defense systems, including DNA damage response (DDR) and DNA repair systems, have developed to protect plant cells. In Arabidopsis, the transcription factor SUPPRESSOR OF GAMMA RESPONSE 1 (SOG1) has been reported to play a key role in DDR. Here, we focus on DDR in rice--thought to be a simpler system compared with Arabidopsis due to lack of induction of endocycle even under DNA damage stress. Rice SOG1 (OsSOG1) and SOG1-like (OsSGL) were identified as putative AtSOG1 orthologs with complete or partial conservation of the serine-glutamine (SQ) motifs involved in activation via phosphorylation. In addition to OsSOG1- or OsSGL-knockout mutants, OsSOG1 non-phosphorylatable mutants (OsSOG1-7A) were generated by homologous recombination-mediated gene targeting. Based on DNA damage susceptibility and transcriptome analysis using these mutants, we demonstrated that OsSOG1, but not OsSGL, plays a central role in the DDR and DNA repair. OsSOG1 regulated target genes via CTT (N)7 AAG motifs reported previously as AtSOG1 recognition sites. The loss of transcription activities and DNA damage tolerance of OsSOG1-7A was not complete compared with OsSOG1-knockout mutants, raising the possibility that another phosphorylation site might be involved in the activation of OsSOG1. Furthermore, our findings have highlighted differences in SOG1-mediated DDR between rice and Arabidopsis, especially regarding induction of cell-cycle arrest and endocycle arrest, revealing rice-specific DDR mechanisms. One sentence summaryRice transcription factor SUPPRESSOR OF GAMMA RESPONSE 1 controls DNA damage response and DNA repair through activation via phosphorylation and the direct regulation of expression of numerous genes.