title: Rice CYP703A3, a cytochrome P450 hydroxylase, is essential for development of anther cuticle and pollen exine.
abstract: 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.
authors.affiliation: State Key Laboratory of Hybrid Rice, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Xijia
authors.initials: X
authors.lastname: Yang
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.forename: Jianxin
authors.initials: J
authors.lastname: Shi
authors.forename: Yi
authors.initials: Y
authors.lastname: He
authors.forename: Franck
authors.initials: F
authors.lastname: Pinot
authors.forename: Bernard
authors.initials: B
authors.lastname: Grausem
authors.forename: Changsong
authors.initials: C
authors.lastname: Yin
authors.forename: Lu
authors.initials: L
authors.lastname: Zhu
authors.forename: Mingjiao
authors.initials: M
authors.lastname: Chen
authors.forename: Zhijing
authors.initials: Z
authors.lastname: Luo
authors.forename: Wanqi
authors.initials: W
authors.lastname: Liang
authors.forename: Dabing
authors.initials: D
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D035264:Flowers / Q000254:growth & development*; D007850:Lauric Acids / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D010641:Phenotype; D010940:Plant Proteins / Q000378:metabolism*; D014885:Waxes / Q000378:metabolism
chemical_list: D007850:Lauric Acids; D008563:Membrane Lipids; D010940:Plant Proteins; D014885:Waxes; C030358:lauric acid; C000521:cutin; D003577:Cytochrome P-450 Enzyme System
keywords: 7-hydroxylated lauric acid; Anther cuticle; CYP703A3; cytochrome P450 hydroxylase; pollen exine