BROWN-MIDRIB MAIZE (BM1) - A MUTATION AFFECTING THE CINNAMYL ALCOHOL-DEHYDROGENASE GENE

Brown-midrib (bm) mutants of maize have modified lignin of reddish-bro wn colour. Although four independent bm loci are known, only one of th e mutant genes has been previously identified. We report here that mai ze bm1, one of the less characterised mutants, shows severely reduced CAD activity in lignified tissues, resulting in the production of a mo dified 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 gen e. CAD maps very closely to the known location of bm1 and co-segregate s with the bm1 locus in two independent recombinant inbred populations . These data strongly support the premise that maize bm1 directly affe cts expression of the CAD gene.