Genome-Wide Identification of the SRZ Gene Family in Rice and Arabidopsis, and Functional Analysis of OsSRZ1 in Regulating Panicle Exsertion

The Stress-Repressive Zinc Finger (SRZ) family is a class of zinc finger proteins in plants that has been closely associated with plant growth, development, and stress responses. In this study, we conducted a genome-wide identification of the SRZ family members and identified 14 and 10 members in rice and Arabidopsis, respectively. We further characterized their phylogenetic relationships, gene structures, conserved motifs, promoter cis-elements, synteny, and spatiotemporal expression patterns. To investigate the functional role of this family in rice, we generated targeted mutants of OsSRZ1 using the CRISPR/Cas9 system. Phenotypic analysis revealed that srz1 knockout mutants exhibited significantly reduced plant height. Notably, the homozygous mutant srz1 completely failed in panicle exsertion from the flag leaf sheath, resulting in complete enclosure, whereas the heterozygous mutant srz1(h) exhibited only partial panicle exsertion. Further cytological observations revealed abnormal floral organ development and premature anther senescence in srz1, accompanied by a significant reduction in seed setting rate—srz1(h) set significantly fewer seeds, whereas srz1 exhibited complete sterility with a seed setting rate of 0%. Collectively, these findings suggest that members of the SRZ family may play important roles in rice growth and development. Our results demonstrate that OsSRZ1 is a critical regulator of plant height and panicle exsertion by regulating internode elongation, and that its disruption leads to premature anther programmed cell death (PCD) and consequent seed setting failure.