Altered Meristem Initiation Is Associated with Increased OSHB3 Expression in a Semi-Dominant Rice Mutant

HD-ZIP III genes encode important transcription factors that play a crucial role in plant development and are regulated by microRNAs (miRNA). Although previous studies have examined the functions of rice HD-ZIP III genes using overexpression lines, the developmental consequences of increased expression of the rice OSHB3 gene under native regulatory conditions remain unclear. In this study, we isolated a gain-of-function mutant carrying mutations in the miRNA target site of the OSHB3 gene, a member of the HD-ZIP III family, and examined its morphology at multiple developmental stages. Gene expression was analyzed using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and in situ hybridization. Our results reveal that ectopic expression of the OSHB3 gene is associated with the differentiation pattern of meristems in rice and that a correlation exists between OSHB3 expression levels and phenotypic severity in the mutants. These findings highlight the importance of precise spatial and quantitative regulation of HD-ZIP III genes in rice development.