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Glycerol-3-phosphate acyltransferases (GPATs), critical for multiple biological processes like male fertility, have been extensively characterized. However, their precise functions and underlying regulatory mechanism in cotton anther development are unclear. This research demonstrated the importance of GhGPAT12/25 (a paralogs pair on A12/D12 sub-chromosome of cotton) to regulate the degradation of tapetum, anther cuticle formation, and pollen exine development. GhGPAT12 and GhGPAT25 exhibited specifically detected transcripts in tapetum and pollen exine during the early anther developmental stages. GhGPAT12/25 are sn-2 glycerol-3-phosphate acyltransferases and can transfer the acyl group of palmitoyl-CoA to glycerol-3-phosphate (G3P). CRISPR/Cas9-mediated knockout identified the functional redundancy of GhGPAT12 and GhGPAT25. Knockout of both genes caused completely male sterility associated with abnormal anther cuticle, swollen tapetum, and inviable microspores with defective exine and irregular unrestricted shape. RNA-seq analysis showed that the loss of function of GhGPAT12/25 affects the processes of wax metabolic, glycerol monomer biosynthesis, and transport. Consistently, cuticular waxes were dramatically reduced in mutant anthers. Yeast one-hybrid system (Y1H), virus-induced gene silencing (VIGS), and dual-luciferase (LUC) assays illustrated that GhMYB80s are likely to directly activate the expression of GhGPAT12/25. This study provides important insights for revealing the regulatory mechanism underlying anther development in cotton.

Wax, cutin and sporopollenin are essential components for the formation of the anther cuticle and the pollen exine, respectively. Their lipid precursors are synthesized by secretory tapetal cells and transported to the anther and microspore surface for deposition. However, the molecular mechanisms involved in the formation of the anther cuticle and pollen exine are poorly understood in rice. Here, we characterized a rice male sterile mutant osabcg26. Molecular cloning and sequence analysis revealed a point mutation in the gene encoding an ATP binding cassette transporter G26 (OsABCG26). OsABCG26 was specifically expressed in the anther and pistil. Cytological analysis revealed defects in tapetal cells, lipidic Ubisch bodies, pollen exine, and anther cuticle in the osabcg26 mutant. Expression of some key genes involved in lipid metabolism and transport, such as UDT1, WDA1, CYP704B2, OsABCG15, OsC4 and OsC6, was significantly altered in osabcg26 anther, possibly due to a disturbance in the homeostasis of anther lipid metabolism and transport. Additionally, wild-type pollen tubes showed a growth defect in osabcg26 pistils, leading to low seed setting in osabcg26 cross-pollinated with the wild-type pollen. These results indicated that OsABCG26 plays an important role in anther cuticle and pollen exine formation and pollen-pistil interactions in rice.

Background Sporopollenin is a major component of the pollen exine pattern. In Arabidopsis, acyl-CoA synthetase5 (ACOS5) is involved in sporopollenin precursor biosynthesis. In this study, we identified its orthologue, OsACOS12, in rice (Oryza sativa) and compared the functional conservation of ACOS in rice to Arabidopsis. Results Sequence analysis showed that OsACOS12 shares 63.9 % amino acid sequence identity with ACOS5. The osacos12 mutation caused by a pre-mature stop codon in LOC_Os04g24530 exhibits defective sexine resulting in a male sterile phenotype in rice. In situ hybridization shows that OsACOS12 is expressed in tapetal cells and microspores at the transcript level. The localization of OsACOS12-GFP demonstrated that OsACOS12 protein is accumulated in tapetal cells and anther locules. OsACOS12 driven by the ACOS5 promoter could partially restore the male fertility of the acos5 mutant in Arabidopsis. Conclusions OsACOS12 is an orthologue of ACOS5 that is essential for sporopollenin synthesis in rice. ACOS5 and OsACOS12 are conserved for pollen wall formation in monocot and dicot species. Electronic supplementary material The online version of this article (doi:10.1186/s12870-016-0943-9) contains supplementary material, which is available to authorized users.