Brown‐midrib maize (bm1) – a mutation affecting the cinnamyl alcohol dehydrogenase gene

Abstract

SummaryBrown-midrib (bm) mutants of maize have modified lignin of reddish-brown colour. Although four independent bm loci are known, only one of the mutant genes has been previously identified. We report here that maize bm1, one of the less characterised mutants, shows severely reduced CAD activity in lignified tissues, resulting in the production of a modified lignin. Both the total lignin content and the structure of the polymer are altered by the mutation. We further describe the isolation and characterisation of the maize CAD cDNA and mapping of the CAD gene. CAD maps very closely to the known location of bm1 and co-segregates with the bm1 locus in two independent recombinant inbred populations. These data strongly support the premise that maize bm1 directly affects expression of the CAD gene.

Genetic background impacts soluble and cell wall-bound aromatics in brown midrib mutants of sorghum

“…However, the exact mechanisms behind these observations remain to be investigated. The maize brown midrib mutant Bm-1 is phenotypically similar to sorghum bmr-6 (Halpin et al 1998). In Bm-1, CAD activity is reduced, but not eliminated, and Bm-1 has been mapped to a region of the maize genome containing a CAD homolog (Halpin et al 1998).…”

“…The maize brown midrib mutant Bm-1 is phenotypically similar to sorghum bmr-6 (Halpin et al 1998). In Bm-1, CAD activity is reduced, but not eliminated, and Bm-1 has been mapped to a region of the maize genome containing a CAD homolog (Halpin et al 1998). The sorghum bmr-6 mutation has important consequences on stem phenolic and lignin content, and the future cloning and characterization of BMR-6 and bmr-6 alleles should provide greater biochemical and genetic insights.…”

The maize Brown midrib1 locus affects cell wall composition and plant development in a dose-dependent manner

“…Heredity (2002) 88, 450-457. DOI: 10.1038/sj/hdy/6800078 brightly in the Wiesner reaction (Provan et al, 1997;Halpin et al, 1998). The Wiesner reaction is based on the formation of a red chromophore resulting from the reaction between phloroglucinol and coniferaldehyde end groups under acidic conditions (Geiger and Fuggerer, 1979;Provan et al, 1997).…”

“…The Wiesner reaction is based on the formation of a red chromophore resulting from the reaction between phloroglucinol and coniferaldehyde end groups under acidic conditions (Geiger and Fuggerer, 1979;Provan et al, 1997). The changes in lignin composition in the bm1 mutant are correlated with a reduced activity of the enzyme cinnamyl alcohol dehydrogenase (CAD) (Halpin et al, 1998). The bm2 mutant has a reduction in guaiacyl residues (Chabbert et al, 1994) and a disturbance in the tissue-specific patterns of lignification (Vermerris and Boon, 2001).…”

Genetic and physical fine mapping of the novel brown midrib gene bm6 in maize (Zea mays L.) to a 180 kb region on chromosome 2

“…Reduced content of sinapyl residues, thus an increased G/S ratio, and elevated level of 5-hydroxyconiferyl alcohol content in lignin were also observed in bm3 plants (Chabbert et al 1994a;Provan et al 1997;Marita et al 2003). bm1 was associated with reduced activity of cinnamyl alcohol dehydrogenase 2 (CAD2) gene (Halpin et al 1998). CAD is responsible for converting hydroxycinnamylaldehydes into alcohols in monolignol biosynthesis (Guillaumie et al 2007b).…”