MALE STERILE6021 (MS6021) is required for the development of anther cuticle and pollen exine in maize

Youhui Tian,Juan Liu,Mingming Wang,Li Zhao,Huairen Zhang,Hua Zhang,Senlin Xiao,Yamuna Somaratne,Huabang Chen

doi:10.1038/s41598-017-16930-0

Youhui Tian, Juan Liu + Show 7 more

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https://doi.org/10.1038/s41598-017-16930-0

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Abstract

The anther cuticle and pollen wall function as physical barriers that protect genetic material from various environmental stresses. The anther cuticle is composed of wax and cutin, the pollen wall includes exine and intine, and the components of the outer exine are collectively called sporopollenin. Other than cuticle wax, cutin and sporopollenin are biopolymers compounds. The precise constituents and developmental mechanism of these biopolymeric are poorly understood. Here, we reported a complete male sterile mutant, male sterile6021, in maize. The mutant displayed a smooth anther surface and irregular pollen wall formation before anthesis, and its tapetum was degraded immaturely. Gas chromatography-mass spectrometry analysis revealed a severe reduction of lipid derivatives in the mutant anther. We cloned the gene by map based cloning. It encoded a fatty acyl carrier protein reductase that was localized in plastids. Expression analysis indicated that MS6021 was mainly expressed in the tapetum and microspore after the microspore was released from the tetrad. Functional complementation of the orthologous Arabidopsis mutant demonstrated that MS6021 is conserved between monocots and dicots and potentially even in flowering plants. MS6021 plays a conserved, essential role in the successful development of anther cuticle and pollen exine in maize.

Highlights

In flowering plants, male reproductive development is essential for metagenesis and genetic recombination, which is a complex process in which cooperative interactions occur between sporophytic and gametophytic tissues[1,2]
ACYL COENZYME A SYNTHETASE 524, two POLYKETIDE SYNTHESES, PKSA/LAP6 and PKSB/LAP525,26, TETRAKETIDE α-PYRONE REDUCTASE 1 (TKPR1)[27,28] are proposed to function together in the synthesis of hydroxylated tetraketide α-pyrones, which are polyketides that may form the major constituent of sporopollenin[29]
To identify maize genes that contribute to anther development, we requested a series of male sterile mutants from the stock at maizeGDB

Summary

Introduction

Male reproductive development is essential for metagenesis and genetic recombination, which is a complex process in which cooperative interactions occur between sporophytic and gametophytic tissues[1,2]. As a secretory cell layer, the tapetum provides abundant ingredients for the anther cuticle and pollen outer wall[5,6]. Recent genetic and biochemical investigations of the development of Arabidopsis and rice anthers have greatly facilitated our understanding of the synthesis regulation of aliphatic biopolymers, such as anther cuticle and sporopollenin[17]. These precursors must be secreted from the tapetum and transferred to the outside surface of microspores and anther wall surfaces to be polymerized into biopolymers of sporopollenin, and cutin[30] respectively. It is speculated to transfer lipidic molecules from tapetal cells to other anther cells and pollen wall surfaces because the mutant displays both defective cuticle and exine development[33]. ABNORMAL POLLEN VACUOLATION1 encodes another P450 family protein that functions in the fatty acid hydroxylation pathway[37]. This work would improve our understanding of anther cuticle and exine development in maize

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