Abstract
BackgroundSporopollenin 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.ResultsSequence 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 materialThe online version of this article (doi:10.1186/s12870-016-0943-9) contains supplementary material, which is available to authorized users.
Highlights
Sporopollenin is a major component of the pollen exine pattern
The large superfamily of acyl-activating enzymes contains putative motifs for AMP-binding and fatty acidbinding [29, 30]. These motifs are highly conserved between OsACOS12 and acyl-CoA synthetase5 (ACOS5) (Fig. 1a)
Sequence analysis demonstrated that acyl-CoA synthetase (ACOS) enzymes are apparently present in land plants, which supports a possible role for them in the biosynthesis of sporopollenin, which is the demand for protecting gametophytes to adapt to a land environment
Summary
Sporopollenin is a major component of the pollen exine pattern. Male reproductive development is an essential biological process for the propagation of flowering plants. Pollen development is the major event of male reproduction. Pollen wall formation is a key process required for pollen viability and male fertility. The pollen wall structure divides into the outer exine and the inner intine. The exine is further divided into a species-specific sexine and a flat nexine [2]. The major composition of the sexine is sporopollenin [3], while the nexine is mainly composed of glycoproteins [4]. The biological function of the sexine layer is to provide an external barrier for adapting the terrestrial environment to ensure microgamete survival in land plants to resist various environmental stresses and microbial
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