Anther cuticle and pollen exine act as protective envelopes for the male gametophyte or pollen grain, but the mechanism underlying the synthesis of these lipidic polymers remains unclear. Previously, a tapetum‐expres...Anther cuticle and pollen exine act as protective envelopes for the male gametophyte or pollen grain, but the mechanism underlying the synthesis of these lipidic polymers remains unclear. Previously, a tapetum‐expressed CYP703A3, a putative cytochrome P450 fatty acid hydroxylase, was shown to be essential for male fertility in rice（Oryza sativa L.）. However,the biochemical and biological roles of CYP703A3 has not been characterized. Here, we observed that cyp703a3‐2 caused by one base insertion in CYP703A3 displays defective pollen exine and anther epicuticular layer, which differs from Arabidopsis cyp703a2 in which only defective pollen exine occurs. Consistently, chemical composition assay showed that levels of cutin monomers and wax components were dramatically reduced in cyp703a3‐2 anthers. Unlike the wide range of substrates of Arabidopsis CYP703A2, CYP703A3 functions as an in‐chain hydroxylase only for a specific substrate, lauric acid, preferably generating 7‐hydroxylated lauric acid. Moreover, chromatin immunoprecipitation and expression analyses revealed that the expression of CYP703A3 is directly regulated by Tapetum Degeneration Retardation, a known regulator of tapetum PCD and pollen exine formation. Collectively, our results suggest that CYP703A3 represents a conserved and diversified biochemical pathway for in‐chain hydroxylation of lauric acid required for the development of male organ in higher plants.展开更多
基金supported by funds from National Natural Science Foundation of China (31230051, 30971739, 31270222, and 31110103915)National Key Basic Research Developments Program, Ministry of Science and Technology, China (2013CB126902 and 2011CB100101)+2 种基金China Innovative Research Team, Ministry of Education111 Project (B14016)the 863 High‐Tech Project, Ministry of Science and Technology, China (2011AA10A101 and 2012AA10A302)
文摘Anther cuticle and pollen exine act as protective envelopes for the male gametophyte or pollen grain, but the mechanism underlying the synthesis of these lipidic polymers remains unclear. Previously, a tapetum‐expressed CYP703A3, a putative cytochrome P450 fatty acid hydroxylase, was shown to be essential for male fertility in rice（Oryza sativa L.）. However,the biochemical and biological roles of CYP703A3 has not been characterized. Here, we observed that cyp703a3‐2 caused by one base insertion in CYP703A3 displays defective pollen exine and anther epicuticular layer, which differs from Arabidopsis cyp703a2 in which only defective pollen exine occurs. Consistently, chemical composition assay showed that levels of cutin monomers and wax components were dramatically reduced in cyp703a3‐2 anthers. Unlike the wide range of substrates of Arabidopsis CYP703A2, CYP703A3 functions as an in‐chain hydroxylase only for a specific substrate, lauric acid, preferably generating 7‐hydroxylated lauric acid. Moreover, chromatin immunoprecipitation and expression analyses revealed that the expression of CYP703A3 is directly regulated by Tapetum Degeneration Retardation, a known regulator of tapetum PCD and pollen exine formation. Collectively, our results suggest that CYP703A3 represents a conserved and diversified biochemical pathway for in‐chain hydroxylation of lauric acid required for the development of male organ in higher plants.
