title: Male Sterile2 encodes a plastid-localized fatty acyl carrier protein reductase required for pollen exine development in Arabidopsis.
abstract: Male Sterile2 (MS2) is predicted to encode a fatty acid reductase required for pollen wall development in Arabidopsis (Arabidopsis thaliana). Transient expression of MS2 in tobacco (Nicotiana benthamiana) leaves resulted in the accumulation of significant levels of C16 and C18 fatty alcohols. Expression of MS2 fused with green fluorescent protein revealed that an amino-terminal transit peptide targets the MS2 to plastids. The plastidial localization of MS2 is biologically important because genetic complementation of MS2 in ms2 homozygous plants was dependent on the presence of its amino-terminal transit peptide or that of the Rubisco small subunit protein amino-terminal transit peptide. In addition, two domains, NAD(P)H-binding domain and sterile domain, conserved in MS2 and its homologs were also shown to be essential for MS2 function in pollen exine development by genetic complementation testing. Direct biochemical analysis revealed that purified recombinant MS2 enzyme is able to convert palmitoyl-Acyl Carrier Protein to the corresponding C16:0 alcohol with NAD(P)H as the preferred electron donor. Using optimized reaction conditions (i.e. at pH 6.0 and 30°C), MS2 exhibits a K(m) for 16:0-Acyl Carrier Protein of 23.3 ± 4.0 μm, a V(max) of 38.3 ± 4.5 nmol mg⁻¹ min⁻¹, and a catalytic efficiency/K(m) of 1,873 M⁻¹ s⁻¹. Based on the high homology of MS2 to other characterized fatty acid reductases, it was surprising that MS2 showed no activity against palmitoyl- or other acyl-coenzyme A; however, this is consistent with its plastidial localization. In summary, genetic and biochemical evidence demonstrate an MS2-mediated conserved plastidial pathway for the production of fatty alcohols that are essential for pollen wall biosynthesis in Arabidopsis.
authors.affiliation: Institute of Plant Science, State Key Laboratory of Hybrid Rice, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Chen
authors.forename: Xiao-Hong
authors.initials: XH
authors.lastname: Yu
authors.forename: Kaisi
authors.initials: K
authors.lastname: Zhang
authors.forename: Jianxin
authors.initials: J
authors.lastname: Shi
authors.forename: Sheron
authors.initials: S
authors.lastname: De Oliveira
authors.forename: Lukas
authors.initials: L
authors.lastname: Schreiber
authors.forename: John
authors.initials: J
authors.lastname: Shanklin
authors.forename: Dabing
authors.initials: D
authors.lastname: Zhang
mesh_terms: D017360:Arabidopsis / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics; D018087:Plastids / Q000378:metabolism*; D011058:Pollen / Q000254:growth & development* / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C109354:MS2 protein, Arabidopsis; D049452:Green Fluorescent Proteins; D009249:NADP