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 , 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. was preferentially expressed during stamen development, and mutation of resulted in male sterility. OsTGA10 was required for tapetum development and functioned by interacting with known tapetum genes. In addition, in 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 implies that cell wall thickening of endothecium is dependent on tapetum development.

OsGPAT3 Plays a Critical Role in Anther Wall Programmed Cell Death and Pollen Development in Rice

“…Premature or delayed tapetal PCD and cellular degeneration can cause pollen abortion and male sterility [2,9,12,15]. Recently, multiple genes were identified to play essential roles in the process of rice tapetal PCD and pollen development, including several basic helix–loop–helix ( bHLH ) transcription factors, undeveloped tapetum 1 ( UDT1 , bHLH164 ) [11], tapetum degeneration retardation ( TDR , bHLH5 ) [12,18], eternal tapetum 1/delayed tapetum degeneration ( EAT1 / DTD , bHLH141 ) [19,20], TDR-interacting protein 2 ( TIP2 , bHLH142 ) [21,22,23,24], MYB family transcription factor GAMYB [25,26,27], PHD-finger protein persistent tapetal cell 1 ( PTC1 ) [28], and TGA transcription factor OsTGA10 [29]. These genes were shown to regulate various aspects of anther development, especially tapetal PCD.…”

A point mutation in LTT1 enhances cold tolerance at the booting stage in rice

“…Consistent with the differential changes of the endogenous ROS level induced by cold stress between the mutant and WT, we found that transcription of OsRbohs was all greatly induced in the cold‐stressed anthers of WT, whereas expression of most of these genes was only slightly changed in the anthers of ltt1 under the same cold stress conditions (Figures 4a and S7a). We then surveyed the expression of 11 tapetal PCD genes in the anthers of ltt1 and WT, including OsUDT1 (Jung et al, ), OsTDR1 (Li et al, ), OsMYB80/OsMYB103 (Phan, Li, & Parish, ), OsMADS3 (Hu et al, ), OsPTC1 (Li et al, ), OsEAT1/DTD (Ji et al, ; Niu et al, ), OsTIP2 (Fu et al, ; Ko et al, ), OsDTC1 (Yi et al, ), OsTGA10 (Chen et al, ; Yang et al, ), and OsAGO2/OsHXK1 (Zheng et al, ). We found that under natural growth conditions, some of the tapetal PCD genes, including OsAGO2 and its downstream target OsHKX1 , OsMYB80 , and OsUDT1 , showed enhanced expression in ltt1 compared with that in WT (Figure 4h), which should be due to the inductive effects of the elevated ROS level in the mutant.…”

“…OsUDT1 (Jung et al, 2005), OsTDR1 (Li et al, 2006), OsMYB80/ OsMYB103 (Phan, Li, & Parish, 2012), OsMADS3 (Hu et al, 2011), OsPTC1 (Li et al, 2011, OsEAT1/DTD (Ji et al, 2013;Niu et al, 2013), OsTIP2 (Fu et al, 2014;Ko et al, 2014), OsDTC1 (Yi et al, 2016), OsTGA10 (Chen et al, 2018;Yang et al, 2016), and OsAGO2/ OsHXK1 (Zheng et al, 2019). We found that under natural growth conditions, some of the tapetal PCD genes, including OsAGO2 and its downstream target OsHKX1, OsMYB80, and OsUDT1, showed enhanced expression in ltt1 compared with that in WT (Figure 4h), which should be due to the inductive effects of the elevated ROS level in the mutant.…”

Molecular Cloning of Genic Male-Sterility Genes and Their Applications for Plant Heterosis via Biotechnology-based Male-sterility Systems

“…Therefore, some of the GMS genes could be isolated by other reverse genetic approaches, such as chromatin immunoprecipitation sequencing (ChIP-Seq), genome-wide expression analysis of a specific gene family, targeted mutagenesis of candidate GMS genes, etc. For example, OsTGA10 encoding a bZIP transcription factor was identified as a target of the MADS box protein OsMADS8 by using the ChIP-seq technique, and mutation of OsTGA10 resulted in male sterility [84]. OsSTRL2 was identified based on the genome-wide expression analysis of rice STR-like (OsSTRL) gene family and its anther-specific expression pattern [82].…”

“…Cytological observation methods include light microscopy of transverse sections, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) of anther and pollen development. For instance, the functions of rice OsTGA10 and OsAGO2 in male sterility were confirmed by targeted mutagenesis of these genes with antisense and CRISPR-Cas9 systems and cytological characterization of mutants by transverse section observation and TEM analysis of anthers at different stages [84,85]. The functions of wheat TaMs26 in anther and pollen wall development in bread wheat were tested by targeted mutagenesis of all the three homologs and cytological analysis using SEM method [77].…”