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

Yu Han,Si-Da Zhou,Jiong-Jiong Fan,Zhong-Nan Yang,Lei Zhou,Qiang-Sheng Shi,Yan-Fei Zhang,Xing Chen,Jun Zhu,Xing-Lu Liu

doi:10.1186/s12284-020-00451-y

Abstract

BackgroundDuring 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.ResultsIn 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.ConclusionOverall, 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.

Highlights

During anther development, the tapetum provides essential nutrients and materials for pollen development
Several transcription factors essential for tapetum development have been cloned from male-sterile lines of rice
We sequenced the OsMS188 locus in the malesterile lines in the F2 population. This locus had a mutation in all the lines. These results demonstrate that the target mutations of OsMS188 caused male sterility in the transgenic lines

Summary

Introduction

The tapetum provides essential nutrients and materials for pollen development. Multiple transcription factors and enzymes essential for tapetum development and pollen wall formation have been cloned from male-sterile lines. Heterosis from hybrid breeding significantly increases agricultural yields of rice and other crop species (Chen and Liu 2014). The use of male-sterile plants, which serve as necessary breeding materials, constitutes a convenient approach for producing hybrid varieties. The tapetal layer is in directly contact with developing gametophytes and provides necessary materials and nutrients for microspore development (Mariani et al 1990; McCormick 1993; Ariizumi and Toriyama 2011). Several transcription factors essential for tapetum development have been cloned from male-sterile lines of rice. Undeveloped Tapetum (UDT1) (Jung et al 2005), Tapetum Degeneration (2021) 14:4

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Conclusion