Ostkpr1 functions in anther cuticle development and pollen wall formation in rice

Dawei Xu,Dabing Zhang,Jianxin Shi,Matthew R Tucker,Wanqi Liang,Shuying Qu

doi:10.1186/s12870-019-1711-4

Dawei Xu, Dabing Zhang + Show 4 more

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https://doi.org/10.1186/s12870-019-1711-4

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Abstract

BackgroundDuring pollen wall formation in flowering plants, a conserved metabolon consisting of acyl-CoA synthetase (ACOS), polyketide synthase (PKS) and tetraketide α-pyrone reductase (TKPR), is required for sporopollenin synthesis. Despite this, the precise function of each of these components in different species remains unclear.ResultsIn this study, we characterized the function of OsTKPR1, a rice orthologue of Arabidopsis TKPR1. Loss of function of OsTKPR1 delayed tapetum degradation, reduced the levels of anther cuticular lipids, and impaired Ubisch body and pollen exine formation, resulting in complete male sterility. In addition, the phenylpropanoid pathway in mutant anthers was remarkably altered. Localization studies suggest that OsTKPR1 accumulates in the endoplasmic reticulum, while specific accumulation of OsTKPR1 mRNA in the anther tapetum and microspores is consistent with its function in anther and pollen wall development.ConclusionsOur results show that OsTKPR1 is indispensable for anther cuticle development and pollen wall formation in rice, providing new insights into the biochemical mechanisms of the conserved sporopollenin metabolon in flowering plants.

Highlights

During pollen wall formation in flowering plants, a conserved metabolon consisting of acyl-CoA synthetase (ACOS), polyketide synthase (PKS) and tetraketide α-pyrone reductase (TKPR), is required for sporopollenin synthesis
Our studies suggest that OsTKPR1 functions in anther cuticle development and pollen wall formation, and reveal some interesting putative differences compared to TKPR1 from Arabidopsis
Isolation and characterization of the ostkpr1–2 mutant Screening of a 60Co γ-ray radiated mutant library in the background of 9522, a cultivar of O. sativa ssp japonica, led to the isolation of a male sterile mutant, ostkpr1–2, which was named based on the results presented below

Summary

Introduction

During pollen wall formation in flowering plants, a conserved metabolon consisting of acyl-CoA synthetase (ACOS), polyketide synthase (PKS) and tetraketide α-pyrone reductase (TKPR), is required for sporopollenin synthesis. The typical pollen wall in flowering plants is composed of two distinct layers: the outer exine and inner intine, with the pollen coat deposited on the surface of the exine [2, 3]. Precursors of sporopollenin are known to be produced and secreted from the tapetal cells to the surface of pollen grains [7]; some evidence demonstrates that pollen grains themselves contribute to sporopollenin biosynthesis and exine formation [8]. The de novo biosynthesis of sporopollenin precursors occurs in plastids, and the deposition of sporopollenin precursors begins soon after the completion of meiosis when the temporary callose wall is degraded and the primexine is formed (stage 9).

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