The maize brown midrib2 (bm2) gene encodes a methylenetetrahydrofolate reductase that contributes to lignin accumulation. (10th January 2014)

• Record Type: Journal Article
• Authors: Tang, Ho Man; Liu, Sanzhen; Hill‐Skinner, Sarah; Wu, Wei; Reed, Danielle; Yeh, Cheng‐Ting; Nettleton, Dan; Schnable, Patrick S.
• Is Part Of: Plant journal. Volume 77:Number 3(2014:Feb.)
• Page Start: 380
• Page End: 392
• Publication Date: 2014-01-10
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12394
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12394-abs-0001"> <title>Summary</title> <p>The midribs of maize <italic>brown midrib</italic> (<italic>bm</italic>) mutants exhibit a reddish‐brown color associated with reductions in lignin concentration and alterations in lignin composition. Here, we report the mapping, cloning, and functional and biochemical analyses of the <italic>bm2</italic> gene. The <italic>bm2</italic> gene was mapped to a small region of chromosome 1 that contains a putative methylenetetrahydrofolate reductase (MTHFR) gene, which is down‐regulated in <italic>bm2</italic> mutant plants. Analyses of multiple <italic>Mu</italic>‐induced <italic>bm2‐Mu</italic> mutant alleles confirmed that this constitutively expressed gene is <italic>bm2</italic>. Yeast complementation experiments and a previously published biochemical characterization show that the <italic>bm2</italic> gene encodes a functional MTHFR. Quantitative RT<italic>‐</italic>PCR analyses demonstrated that the <italic>bm2</italic> mutants accumulate substantially reduced levels of <italic>bm2</italic> transcript. Alteration of MTHFR function is expected to influence accumulation of the methyl donor <italic>S‐</italic>adenosyl‐<sc>l</sc><italic>‐</italic>methionine (SAM). Because SAM is consumed by two methyltransferases in the lignin pathway (Ye <italic>et al</italic>., <xref ref-type="link" rid="tpj12394-bib-0056">1994</xref>), the finding that <italic>bm2</italic> encodes a functional MTHFR is consistent with its lignin phenotype. Consistent with this functional assignment of <italic>bm2</italic>, the expression patterns of genes in a variety of SAM‐dependent or ‐related pathways, including lignin biosynthesis, are altered in the <italic>bm2</italic> mutant. Biochemical assays confirmed that <italic>bm2</italic> mutants accumulate reduced levels of lignin with altered composition compared to wild‐type. Hence, this study demonstrates a role for MTHFR in lignin biosynthesis.</p> </abstract>