Abstract
BackgroundThe anther cuticle, which is primarily composed of lipid polymers, is crucial for pollen development and plays important roles in sexual reproduction in higher plants. However, the mechanism underlying the biosynthesis of lipid polymers in maize (Zea mays. L.) remains unclear.ResultsHere, we report that the maize male-sterile mutant shrinking anther 1 (sa1), which is allelic to the classic mutant male sterile 33 (ms33), displays defective anther cuticle development and premature microspore degradation. We isolated MS33 via map-based cloning. MS33 encodes a putative glycerol-3-phosphate acyltransferase and is preferentially expressed in tapetal cells during anther development. Gas chromatography-mass spectrometry revealed a substantial reduction in wax and cutin in ms33 anthers compared to wild type. Accordingly, RNA-sequencing analysis showed that many genes involved in wax and cutin biosynthesis are differentially expressed in ms33 compared to wild type.ConclusionsOur findings suggest that MS33 may contribute to anther cuticle and microspore development by affecting lipid polyester biosynthesis in maize.
Highlights
The anther cuticle, which is primarily composed of lipid polymers, is crucial for pollen development and plays important roles in sexual reproduction in higher plants
C16:0 acid, C18:2 acid, C16:0 16-OH acid, C22:0 2-OH acid, and C24:0 2-OH acid are the major types of aliphatic cutin monomers in anthers. The levels of these monomers were substantially reduced in ms33 compared to wild type (Fig. 7c, Additional file 3: Table S2). These results suggest that MS33 may play an important role in the biosynthesis of wax and cutin monomers, which are essential for normal development of the anther cuticle and pollen grains
Using the gas chromatography-mass spectrometry (GC-MS), substantial reduction in wax and cutin were detected in ms33
Summary
The anther cuticle, which is primarily composed of lipid polymers, is crucial for pollen development and plays important roles in sexual reproduction in higher plants. Each male floret has three anthers, each with four lobes These four lobes have similar structures and are attached to a central core connected to the vascular tissue. From the exterior to the interior, the centrally located microspores are covered by the epidermis, endothecium, middle layer, and tapetum [1, 2]. The tapetum contributes to microspore development by providing energy and structural materials [3,4,5]. The main component of the pollen exine is sporopollenin, a biopolymer formed by lipid monomers covalently coupled by ether and ester linkages. After meiosis in the anther is complete, sporopollenin is secreted by the tapetum, transported to the microspore surface, and used for pollen exine formation [9, 10]
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