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The maize brown midrib4 ( bm4) gene encodes a functional folylpolyglutamate synthase
Author(s) -
Li Li,
HillSkinner Sarah,
Liu Sanzhen,
Beuchle Danielle,
Tang Ho Man,
Yeh ChengTing,
Nettleton Dan,
Schnable Patrick S.
Publication year - 2015
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12745
Subject(s) - complementation , mutant , gene , biology , genetics , phenotype , yeast , lignin , gene expression , starch synthase , microbiology and biotechnology , biochemistry , botany , amylopectin , amylose , starch
Summary 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, GRMZM 2G393334, showed decreased expression in mutants. At least four of 10 Mu ‐induced bm4 mutant alleles contain a Mu insertion in the GRMZM 2G393334 gene. Based on these results, we concluded that GRMZM 2G393334 is the bm4 gene. GRMZM 2G393334 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.