Open AccessThe global nitrogen regulator, FNR1, regulates fungal nutrition‐genes and fitness during Fusarium oxysporum pathogenesis
Author(s) -
DIVON HEGE HVATTUM,
ZIV CARMIT,
DAVYDOV OLGA,
YARDEN ODED,
FLUHR ROBERT
Publication year - 2006
Publication title -
molecular plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.945
H-Index - 103
eISSN - 1364-3703
pISSN - 1464-6722
DOI - 10.1111/j.1364-3703.2006.00354.x
Subject(s) - biology , neurospora crassa , fusarium oxysporum , gibberella fujikuroi , mutant , gene , xylem , microbiology and biotechnology , virulence , genetics , fusarium , botany
SUMMARY Fusarium oxysporum is a soil‐borne pathogen that infects plants through the roots and uses the vascular system for host ingress. Specialized for this route of infection, F. oxysporum is able to adapt to the scarce nutrient environment in the xylem vessels. Here we report the cloning of the F. oxysporum global nitrogen regulator, Fnr1 , and show that it is one of the determinants for fungal fitness during in planta growth. The Fnr1 gene has a single conserved GATA‐type zinc finger domain and is 96% and 48% identical to AREA‐GF from Gibberella fujikuroi , and NIT2 from Neurospora crassa , respectively. Fnr1 cDNA, expressed under a constitutive promoter, was able to complement functionally an N. crassa nit‐2 RIP mutant, restoring the ability of the mutant to utilize nitrate. Fnr1 disruption mutants showed high tolerance to chlorate and reduced ability to utilize several secondary nitrogen sources such as amino acids, hypoxanthine and uric acid, whereas growth on favourable nitrogen sources was not affected. Fnr1 disruption also abolished in vitro expression of nutrition genes , normally induced during the early phase of infection. In an infection assay on tomato seedlings, infection rate of disruption mutants was significantly delayed in comparison with the parental strain. Our results indicate that FNR1 mediates adaptation to nitrogen‐poor conditions in planta through the regulation of secondary nitrogen acquisition, and as such acts as a determinant for fungal fitness during infection.