Characterization of genes in Fusarium verticillioides regulating colonization of maize kernels

• Published in: Phytopathology Vol. 100; no. 6; p. S148
• Main Authors: Hirsch, R L, Bluhm, B H
• Format: Journal Article
• Language: English
• Published: 01-06-2010
• Subjects: Fusarium verticillioides; Zea mays
• ISSN: 0031-949X

Fusarium verticillioides is a common seedborne pathogen of maize and produces fumonisin mycotoxins during kernel colonization. Identifying genes underlying seed infection is crucial to elucidate pathogenesis at the molecular level. The objective of this research was to characterize genes in F. verticillioides that regulate kernel colonization. The overall approach was to identify genes through forward genetics and determine their function through targeted disruption. First, a collection of >3000 random insertional mutants was generated via Restriction Enzyme Mediated Integration (REMI) with a novel promoter-trapping cassette. A high throughput in vitro screen was developed to quantify the hydrolysis of starch, the predominant carbohydrate in maize kernels. Nine mutants with altered starch hydrolysis were analyzed for their ability to colonize maize kernels; of these, one mutant was significantly impaired in kernel colonization and fumonisin production. In this mutant, the REMI cassette disrupted a gene encoding a putative ubiquitin ligase (designated UBL1). Targeted disruption of UBL1 in the wild-type strain confirmed the phenotype of the REMI mutant. The discovery of a novel regulatory gene underlying seed colonization and fumonisin biosynthesis significantly expands the working model of kernel pathogenesis in F. verticillioides.