Pheromones trigger filamentous growth in Ustilago maydis.

Abstract

Cell recognition and mating in the smut fungus Ustilago maydis have been proposed to involve specific pheromones and pheromone receptors. The respective structural genes are located in the a mating type locus that exists in the alleles a1 and a2. We demonstrate that binding of pheromone to the receptor can induce a morphological switch from yeast‐like to filamentous growth in certain strains. Using this as biological assay we were able to purify both the a1 and a2 pheromone. The structure of the secreted pheromones was determined to be 13 amino acids for a1 and nine amino acids for a2. Both pheromones are post‐translationally modified by farnesylation and carboxyl methyl esterification of the C‐terminal cysteine. An unmodified a1 peptide exhibits dramatically reduced activity. The pheromone alone is able to induce characteristic conjugation tubes in cells of opposite mating type and confers mating competence; even cells of the same mating type undergo fusion. We discuss the role of pheromones in initiating filamentous growth and pathogenic development.

Fuz1, a MYND domain protein, is required for cell morphogenesis inUstilago maydis

“…Cell fusion and filamentous growth can be assayed independently with the appropriate strains (see for example Herskowitz 1989,1994a;Dürrenberger and Kronstad 1999,Gold et al 1994,Regenfelder et al 1997,Spellig et al 1994. Before cell fusion cells form conjugation tubes, a morphological differentiation that occurs in response to pheromones produced by cells of opposite mating type (Banuett and Herskowitz 1994a,b;Snetselaar et al 1996,Spellig et al 1994. To determine if fuz1 is required for conjugation tube formation, we assayed this process in coculture of different strains in low nitrogen medium containing charcoal (see MATERIALS AND METHODS; Banuett and Herskowitz 1994a,b).…”

“…Conjugation tube formation occurs in response to pheromones produced by cells of opposite mating type. This response requires different a alleles but is independent of the b locus (Banuett and Herskowitz 1994a, b;Snetselaar et al 1996, Spellig et al 1994. Thus fuz1 participates in this a-locus dependent pathway.…”

“…Filamentous growth of diploids and dikaryons on charcoal agar requires different a and b alleles Herskowitz 1989, 1994b;Bölker et al 1992, Day et al 1971, Holliday 1961, Puhalla 1968, Ruiz-Herrera et al 1995, Spellig et al 1994. Diploids homozygous at a and heterozygous at b or homozygous at b and heterozygous at a are nonmycelial (Banuett and Herskowitz 1989, Day et al 1971, Holliday 1961, Puhalla 1968.…”

“…The a locus has two alleles, a1 and a2 (Rowell and DeVay 1954); each contains a pheromone precursor and pheromone receptor gene that regulate conjugation tube formation and cell fusion of haploid strains (Banuett and Herskowitz 1994a, b;Snetselaar et al 1996, Spellig et al 1994 and filamentous growth on charcoal agar (Banuett and Herskowitz 1989, Spellig et al 1994 but not in planta Herskowitz 1996, Regenfelder et al 1997). The b locus is multiallelic with at least 25 naturally occurring alleles (Puhalla 1970, Rowell andDeVay 1954;reviewed in Banuett 2007, Holliday 1974, Klosterman et al 2007.…”

Ustilago maydis – a valuable model system for the study of fungal dimorphism and virulence

“…2). The biallelic a locus encodes precursors for specific lipopeptide pheromones and for receptors that can sense the presence of pheromones of opposite mating type Ustilago maydis as a model system and respond to the presence of cells of opposite mating type (Spellig et al, 1994). As a consequence of pheromone recognition, cells arrest in their cell cycle and form conjugation tubes that orient their growth toward the pheromone source (Snetselaar et al, 1996).…”