Identification of Genes Potentially Involved in the Biocontrol Activity of Pseudozyma flocculosa

• Published in: Phytopathology 2009-10, Vol.99 (10), p.1142-1149
• Main Authors: Marchand, G, Rémus-Borel, W, Chain, F, Hammami, W, Belzile, F, Bélanger, R.R
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Base Sequence; Biological and medical sciences; biological control; biosynthesis; Blotting, Southern; cellobiose; Cellobiose - analogs & derivatives; Cellobiose - biosynthesis; Cellobiose - chemistry; Cloning, Molecular; cucumbers; Cucumis sativus; disease control; flocculosin; Fundamental and applied biological sciences. Psychology; fungal antagonists; Fungal Proteins - chemistry; Fungal Proteins - genetics; Fungal Proteins - metabolism; gene expression; Gene Expression Regulation, Fungal; genes; Genes, Fungal; Glycolipids - biosynthesis; Glycolipids - chemistry; lipids; Molecular Sequence Data; nucleotide sequences; Pest Control, Biological; Phylogeny; Phytopathology. Animal pests. Plant and forest protection; plant pathogenic fungi; powdery mildew; Pseudozyma; Pseudozyma flocculosa; Pseudozyma fusiformata; Reverse Transcriptase Polymerase Chain Reaction; Sequence Alignment; Sequence Analysis, DNA; sequence homology; ustilagic acid; Ustilaginales - genetics; Ustilago maydis; Ustilago zeae
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/PHYTO-99-10-1142

Flocculosin is an antifungal cellobiose lipid linked to the biocontrol activity of Pseudozyma flocculosa and whose structure is very similar to that of ustilagic acid produced by Ustilago maydis. In this work, homologs of the U. maydis cyp1 gene, involved in the biosynthesis of ustilagic acid, were isolated and sequenced from P. flocculosa and P. fusiformata, the latter species being also known to produce ustilagic acid. Interestingly, no homologs were found in four other closely related Pseudozyma spp. from which no evidence of ustilagic acid production has ever been obtained, thus supporting the specificity of cyp1 with ustilagic acid synthesis. In addition, a homolog of the U. maydis uat1 gene involved in the acetylation of the molecule and located next to the cyp1 gene was partially sequenced from P. flocculosa. All three newly sequenced genes showed strong sequence similarity to their counterparts in U. maydis. Cyp1 expression was monitored in conditions that were either conducive or repressive to flocculosin production. Expression increased markedly (>100×) when P. flocculosa was inoculated in a growth medium conducive to flocculosin production but was rapidly downregulated in a repressive medium (in vitro) or on powdery mildew-infected cucumber leaves (in vivo). This suggests that the molecule was preferentially synthesized early in the process of searching for a growth substrate. This study provides the first identification of genes involved in the production of flocculosin, a molecule potentially associated with the biocontrol properties of P. flocculosa.