The maize brown midrib4 (bm4) gene encodes a functional folylpolyglutamate synthase |
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| Authors: | Li Li Sarah Hill‐Skinner Sanzhen Liu Danielle Beuchle Ho Man Tang Cheng‐Ting Yeh Dan Nettleton Patrick S. Schnable |
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| Affiliation: | 1. Department of Agronomy, Iowa State University, Ames, IA, USA;2. College of Agronomy, Northwest Agriculture and Forestry University, #3, Taicheng road, Yangling, Shaanxi, 712100, China;3. Department of Genetics, Development and Cell Biology, Iowa State University, 1210 Molecular Biology Building, Ames, IA 50011‐3260, USA;4. Center for Plant Genomics, Iowa State University, Ames, IA, USA;5. Department of Statistics, Iowa State University, Ames, IA, USA |
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| Abstract: | Mutations in the brown midrib4 (bm4) gene affect the accumulation and composition of lignin in maize. Fine‐mapping analysis of bm4 narrowed the candidate region to an approximately 105 kb interval on chromosome 9 containing six genes. Only one of these six genes, GRMZM2G393334, showed decreased expression in mutants. At least four of 10 Mu‐induced bm4 mutant alleles contain a Mu insertion in the GRMZM2G393334 gene. Based on these results, we concluded that GRMZM2G393334 is the bm4 gene. GRMZM2G393334 encodes a putative folylpolyglutamate synthase (FPGS), which functions in one‐carbon (C1) metabolism to polyglutamylate substrates of folate‐dependent enzymes. Yeast complementation experiments demonstrated that expression of the maize bm4 gene in FPGS‐deficient met7 yeast is able to rescue the yeast mutant phenotype, thus demonstrating that bm4 encodes a functional FPGS. Consistent with earlier studies, bm4 mutants exhibit a modest decrease in lignin concentration and an overall increase in the S:G lignin ratio relative to wild‐type. Orthologs of bm4 include at least one paralogous gene in maize and various homologs in other grasses and dicots. Discovery of the gene underlying the bm4 maize phenotype illustrates a role for FPGS in lignin biosynthesis. |
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| Keywords: | brown midrib lignin folylpolyglutamate synthase folylpolyglutamate synthase Zea mays methylenetetrahydrofolate reductase |
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