OsMS188 Is a Key Regulator of Tapetum Development and Sporopollenin Synthesis in Rice

Abstract

Background During anther development, the tapetum provides essential nutrients and materials for pollen development. In rice, multiple transcription factors and enzymes essential for tapetum development and pollen wall formation have been cloned from male-sterile lines. Results In this study, we obtained several lines in which the MYB transcription factor OsMS188 was knocked out through the CRISPR-Cas9 approach. The osms188 lines exhibited a male-sterile phenotype with aberrant development and degeneration of tapetal cells, absence of the sexine layer and defective anther cuticles. CYP703A3, CYP704B2, OsPKS1, OsPKS2, DPW and ABCG15 are sporopollenin synthesis and transport-related genes in rice. Plants with mutations in these genes are male sterile, with a defective sexine layer and anther cuticle. Further biochemical assays demonstrated that OsMS188 binds directly to the promoters of these genes to regulate their expression. UDT1, OsTDF1, TDR, bHLH142 and EAT1 are upstream regulators of rice tapetum development. Electrophoretic mobility shift assays (EMSAs) and activation assays revealed that TDR directly regulates OsMS188 expression. Additionally, protein interaction assays indicated that TDR interacts with OsMS188 to regulate downstream gene expression. Conclusion Overall, OsMS188 is a key regulator of tapetum development and pollen wall formation. The gene regulatory network established in this work may facilitate future investigations of fertility regulation in rice and in other crop species.

The GA–DELLA–OsMS188 module controls male reproductive development in rice

“…Because the slr1‐5 and osms188 mutants share similar anther developmental phenotypes, we compared the gene expression profiles of these two mutants (Han et al ., 2021) (Fig. S3; Table S10).…”

“…DELLA proteins, which do not contain a DNA‐binding domain, generally activate or suppress target gene expression by interacting with other TFs. We noted that the anther development phenotypes and gene expression pattern of osms188 share similarity to those of slr1‐5 (Figs 1, 2, 4) (S. Zhang et al ., 2010; Pan et al ., 2020; Han et al ., 2021; Xiang et al ., 2021). Additionally, the gene expression profile regulated by SLR1 was similar to that regulated by OsMS188 (Fig.…”

“…To prepare yeast two‐hybrid constructs, SLR1 and its truncated fragments were cloned into the Gateway donor vector pEntry‐topo‐SD (primers are listed in Supporting Information Table S1), sequenced and then inserted into the pGADT7GW vector via LR reactions (Invitrogen). Previously described OsMS188‐pGBKT7 and OsMS188ΔC‐pGBKT7 constructs were also used (Han et al ., 2021). To generate bimolecular fluorescence complementation (BiFC) vectors, OsMS188 and SLR1 were cloned into the Gateway donor vector pEntry‐topo‐SD, sequenced, and then inserted into the pSAT4‐nYFP‐C1 and pSAT4‐cYFP‐C1 vectors via LR reactions (Invitrogen).…”

“…It also regulates cell wall transitions, including dissolution of the tetrad wall and formation of the pollen wall, by modulating QRT3 expression (Shi et al ., 2021). Previous research confirmed that AtMYB80/OsMS188 binds directly to the promoters of genes related to sporopollenin synthesis and transport, such as CYP703A3 , OsPKS1 , DPW and ABCG15 , to rapidly promote pollen wall formation (Wang et al ., 2018; Han et al ., 2021). In addition to these TFs, there are other TFs essential for anther development in rice, including TDR‐INTERACTING PROTEIN 2 (TIP2/bHLH142) and TIP3 (Fu et al ., 2014; Ko et al ., 2014; Yang et al ., 2019), ETERNAL TAPETUM 1/DELAYED TAPETUM DEGENERATION (EAT1/DTD/bHLH141) (Ji et al ., 2013; Niu et al ., 2013; Ono et al ., 2018) and OsTGA10 (Chen et al ., 2018).…”

Unraveling the Genetic Basis of Fertility Restoration for Cytoplasmic Male Sterile Line WNJ01A Originated From Brassica juncea in Brassica napus

“…These DEGs included two bHLH TFs ( BHLH089 and BHLH010 ), two extensin peroxidases ( PRX9 and PRX40 ), tapetum-specific TAP35/TAP44 , and two CALS5 genes. During pollen formation, tapetum cells play central roles in callose degradation, pollen exine formation, and the provision of various nutrients for pollen development ( Han et al, 2021 ). Our cytological characterization of the abortive anthers showed that the tapetum cells (which surround the microspores and provide crucial enzymes and nutrients for microsporogenesis and pollen wall development, Ferguson et al, 2017 ) were degraded.…”