The maize brown midrib4 (bm4) gene encodes a functional folylpolyglutamate synthase. (9th January 2015)

• Record Type: Journal Article
• Authors: Li, Li; Hill‐Skinner, Sarah; Liu, Sanzhen; Beuchle, Danielle; Tang, Ho Man; Yeh, Cheng‐Ting; Nettleton, Dan; Schnable, Patrick S.
• Is Part Of: Plant journal. Volume 81:Number 3(2015:Feb.)
• Page Start: 493
• Page End: 504
• Publication Date: 2015-01-09
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12745
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12745-abs-0001"> <title>Summary</title> <p>Mutations in the <italic>brown midrib4 (bm4)</italic> gene affect the accumulation and composition of lignin in maize. Fine‐mapping analysis of <italic>bm4</italic> 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 <italic>Mu</italic>‐induced <italic>bm4</italic> mutant alleles contain a <italic>Mu</italic> insertion in the GRMZM2G393334 gene. Based on these results, we concluded that GRMZM2G393334 is the <italic>bm4</italic> 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 <italic>bm4</italic> gene in FPGS‐deficient <italic>met7</italic> yeast is able to rescue the yeast mutant phenotype, thus demonstrating that <italic>bm4</italic> encodes a functional FPGS. Consistent with earlier studies, <italic>bm4</italic> mutants exhibit a modest decrease in lignin concentration and an overall increase in the S:G lignin ratio relative to wild‐type. Orthologs of <italic>bm4</italic> include at least one paralogous gene in maize and various homologs in other grasses and dicots. Discovery of the gene underlying the <italic>bm4</italic> maize phenotype illustrates a role for FPGS in lignin biosynthesis.</p> </abstract>