title: The Pochonia chlamydosporia serine protease gene vcp1 is subject to regulation by carbon, nitrogen and pH: implications for nematode biocontrol.
abstract: The alkaline serine protease VCP1 of the fungus Pochonia chlamydosporia belongs to a family of subtilisin-like enzymes that are involved in infection of nematode and insect hosts. It is involved early in the infection process, removing the outer proteinaceous vitelline membrane of nematode eggs. Little is known about the regulation of this gene, even though an understanding of how nutrients and other factors affect its expression is critical for ensuring its efficacy as a biocontrol agent. This paper provides new information on the regulation of vcp1 expression. Sequence analysis of the upstream regulatory region of this gene in 30 isolates revealed that it was highly conserved and contained sequence motifs characteristic of genes that are subject to carbon, nitrogen and pH-regulation. Expression studies, monitoring enzyme activity and mRNA, confirmed that these factors affect VCP1 production. As expected, glucose reduced VCP1 expression and for a few hours so did ammonium chloride. Surprisingly, however, by 24 h VCP1 levels were increased in the presence of ammonium chloride for most isolates. Ambient pH also regulated VCP1 expression, with most isolates producing more VCP1 under alkaline conditions. There were some differences in the response of one isolate with a distinctive upstream sequence including a variant regulatory-motif profile. Cryo-scanning electron microscopy studies indicated that the presence of nematode eggs stimulates VCP1 production by P. chlamydosporia, but only where the two are in close contact. Overall, the results indicate that readily-metabolisable carbon sources and unfavourable pH in the rhizosphere/egg-mass environment may compromise nematode parasitism by P. chlamydosporia. However, contrary to previous indications using other nematophagous and entomopathogenic fungi, ammonium nitrate (e.g. from fertilizers) may enhance biocontrol potential in some circumstances.
authors.affiliation: Plant Pathology and Microbiology Department, Rothamsted Research, Harpenden, Herts, United Kingdom. elaine.ward@rothamsted.ac.uk
authors.forename: Elaine
authors.initials: E
authors.lastname: Ward
authors.forename: Brian R
authors.initials: BR
authors.lastname: Kerry
authors.forename: Rosa H
authors.initials: RH
authors.lastname: Manzanilla-López
authors.forename: Gerald
authors.initials: G
authors.lastname: Mutua
authors.forename: Jean
authors.initials: J
authors.lastname: Devonshire
authors.forename: John
authors.initials: J
authors.lastname: Kimenju
authors.forename: Penny R
authors.initials: PR
authors.lastname: Hirsch
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D061046:Biological Control Agents; D002244:Carbon / Q000378:metabolism; D017124:Conserved Sequence; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D054884:Host-Pathogen Interactions; D006863:Hydrogen-Ion Concentration; D006999:Hypocreales / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity; D008969:Molecular Sequence Data; D009348:Nematoda / Q000382:microbiology*; D009566:Nitrates / Q000494:pharmacology; D009584:Nitrogen / Q000378:metabolism; D018517:Plant Roots / Q000469:parasitology; D010944:Plants / Q000469:parasitology; D012331:RNA, Fungal / Q000032:analysis; D057057:Serine Proteases / Q000235:genetics* / Q000378:metabolism; D015053:Zygote / Q000382:microbiology*
chemical_list: D061046:Biological Control Agents; D005656:Fungal Proteins; D009566:Nitrates; D012331:RNA, Fungal; D000643:Ammonium Chloride; D002244:Carbon; D057057:Serine Proteases; D005947:Glucose; D009584:Nitrogen; C006568:ammonium nitrate