The b alleles of U. maydis, whose combinations program pathogenic development, code for polypeptides containing a homeodomain-related motif

Cell. 1990 Jan 26;60(2):295-306. doi: 10.1016/0092-8674(90)90744-y.


U. maydis is a fungal pathogen of corn with two forms: one is yeast-like and nonpathogenic; the other is filamentous and pathogenic. The b locus, with 25 different alleles, regulates this dimorphism: any combination of two different alleles triggers pathogenic development, whereas the presence of identical alleles results in the yeast-like form. We have cloned four b alleles (b1, b2, b3, and b4) and show that the b locus contains a single open reading frame (ORF) of 410 amino acids with a variable N-terminal region and a highly conserved C-terminal region (60% and 93% identity, respectively). Mutational analysis confirms that this ORF is responsible for b activity. The b polypeptides appear to be DNA binding proteins because they contain a motif related to the homeodomain in their constant region. We propose that combinatorial interactions between b polypeptides generate regulatory proteins that determine the developmental program of the fungus.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alleles*
  • Amino Acid Sequence
  • Base Sequence
  • Basidiomycota / genetics*
  • Blotting, Southern
  • Cloning, Molecular
  • DNA, Fungal / genetics
  • DNA, Fungal / isolation & purification
  • Fungal Proteins / genetics
  • Genes, Fungal*
  • Genes, Homeobox*
  • Homozygote
  • Molecular Sequence Data
  • Plasmids
  • Sequence Homology, Nucleic Acid
  • Ustilago / genetics*
  • Ustilago / pathogenicity
  • Zea mays / growth & development


  • DNA, Fungal
  • Fungal Proteins

Associated data

  • GENBANK/M30648
  • GENBANK/M30649
  • GENBANK/M30650
  • GENBANK/M30651
  • GENBANK/M58553
  • GENBANK/M58554
  • GENBANK/M58555
  • GENBANK/M58556