Studies of a rice sterile mutant sstl from the TRIM collection

Yuan-Ching Tsai,Han-Hui Hung,Yan-Cheng Lin,Wann-Neng Jane,Jerry C Serapion,Chia-Ling Chang,Yue-Ie C Hsing,Ming-Hsin Lai,Men-Chi Chang

doi:10.1186/s40529-019-0260-3

Abstract

BackgroundRice (Oryza sativa) is one of the main crops in the world, and more than 3.9 billion people will consume rice by 2025. Sterility significantly affects rice production and leads to yield defects. The undeveloped anthers or abnormal pollen represent serious defects in rice male sterility. Therefore, understanding the mechanism of male sterility is an important task. Here, we investigated a rice sterile mutant according to its developmental morphology and transcriptional profiles.ResultsAn untagged T-DNA insertional mutant showed defective pollen and abnormal anthers as compared with its semi-sterile mutant (sstl) progeny segregates. Transcriptomic analysis of sterile sstl-s revealed several biosynthesis pathways, such as downregulated cell wall, lipids, secondary metabolism, and starch synthesis. This downregulation is consistent with the morphological characterization of sstl-s anthers with irregular exine, absence of intine, no starch accumulation in pollen grains and no accumulated flavonoids in anthers. Moreover, defective microsporangia development led to abnormal anther locule and aborted microspores. The downregulated lipids, starch, and cell wall synthesis-related genes resulted in loss of fertility.ConclusionsWe illustrate the importance of microsporangia in the development of anthers and functional microspores. Abnormal development of pollen grains, pollen wall, anther locule, etc. result in severe yield reduction.

Highlights

Rice (Oryza sativa) is one of the main crops in the world, and more than 3.9 billion people will con‐ sume rice by 2025
TAPETUM DETERMINANT1 (TPD1) interacts with the EXCESS MICROSPOROCYTES1 (EMS1) LRR domain to generate precursors of tapetal cells by promoting cell division of inner secondary parietal layers (SPC); the developmental tapetum layer determines the number of sporogenous cells by suppressing proliferation (Huang et al 2016)
Several regulators respond to microspore generation, and programmed cell death (PCD) of tapetal cells such as a rice basic helix-loop-helix protein, TAPETUM DEGENERATION RETARDATION (TDR), controls tapetum degeneration to contribute to microspore development (Li et al 2006)

Summary

Introduction

Rice (Oryza sativa) is one of the main crops in the world, and more than 3.9 billion people will con‐ sume rice by 2025. Studies of the developmental morphology of pollen revealed several important steps, Chang et al Bot Stud (2019) 60:12 and the inner layer becomes the tapetal cell (Zhang and Wilson 2009). TPD1 interacts with the EMS1 LRR domain to generate precursors of tapetal cells by promoting cell division of inner SPCs; the developmental tapetum layer determines the number of sporogenous cells by suppressing proliferation (Huang et al 2016). The anther with double mutated OSTDL1A and MULTIPLE SPOROCYTE1 genes illustrated a lack of middle layers and tapetum and increased the number of microsporocytes in the early development of pollen (Yang et al 2016). Several regulators respond to microspore generation, and PCD of tapetal cells such as a rice basic helix-loop-helix (bHLH) protein, TAPETUM DEGENERATION RETARDATION (TDR), controls tapetum degeneration to contribute to microspore development (Li et al 2006). With T-DNA insertion into bHLH142, the tapetal PCD and microspore development were defective in anthers of rice loss-of-function bhlh142 (Ko et al 2014)

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Conclusion