Transcription Factor OsTGA10 Is a Target of the MADS Protein OsMADS8 and Is Required for Tapetum Development

Abstract

This study aimed at elucidating regulatory components behind floral organ identity determination and tissue development. It remains unclear how organ identity proteins facilitate development of organ primordia into tissues with a determined identity, even though it has long been accepted that floral organ identity is genetically determined by interaction of identity genes according to the ABC model. Using the chromatin immunoprecipitation sequencing technique, we identified <i>OsTGA10</i>, encoding a bZIP transcription factor, as a target of the MADS box protein OsMADS8, which is annotated as an E-class organ identity protein. We characterized the function of OsTGA10 using genetic and molecular analyses. <i>OsTGA10</i> was preferentially expressed during stamen development, and mutation of <i>OsTGA10</i> resulted in male sterility. OsTGA10 was required for tapetum development and functioned by interacting with known tapetum genes. In addition, in <i>ostga10</i> stamens, the hallmark cell wall thickening of the endothecium was defective. Our findings suggest that OsTGA10 plays a mediator role between organ identity determination and tapetum development in rice stamen development, between tapetum development and microspore development, and between various regulatory components required for tapetum development. Furthermore, the defective endothecium in <i>ostga10</i> implies that cell wall thickening of endothecium is dependent on tapetum development.