title: Oxaloacetate acetylhydrolase gene mutants of Sclerotinia sclerotiorum do not accumulate oxalic acid, but do produce limited lesions on host plants.
abstract: The oxaloacetate acetylhydrolase (OAH, EC 3.7.1.1)-encoding gene Ss-oah1 was cloned and functionally characterized from Sclerotinia sclerotiorum. Ss-oah1 transcript accumulation mirrored oxalic acid (OA) accumulation with neutral pH induction dependent on the pH-responsive transcriptional regulator Ss-Pac1. Unlike previously characterized ultraviolet (UV)-induced oxalate-deficient mutants ('A' mutants) which retain the capacity to accumulate OA, gene deletion Δss-oah1 mutants did not accumulate OA in culture or during plant infection. This defect in OA accumulation was fully restored on reintroduction of the wild-type (WT) Ss-oah1 gene. The Δss-oah1 mutants were also deficient in compound appressorium and sclerotium development and exhibited a severe radial growth defect on medium buffered at neutral pH. On a variety of plant hosts, the Δss-oah1 mutants established very restricted lesions in which the infectious hyphae gradually lost viability. Cytological comparisons of WT and Δss-oah1 infections revealed low and no OA accumulation, respectively, in subcuticular hyphae. Both WT and mutant hyphae exhibited a transient association with viable host epidermal cells at the infection front. In summary, our experimental data establish a critical requirement for OAH activity in S. sclerotiorum OA biogenesis and pathogenesis, but also suggest that factors independent of OA contribute to the establishment of primary lesions.
authors.affiliation: Department of Plant Pathology, University of Florida, Gainesville, FL, 32611-0680, USA.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Liang
authors.affiliation: Nunhems Netherlands BV, PO Box 4005, Haelen, 6080, AA, the Netherlands.
authors.forename: Daniele
authors.initials: D
authors.lastname: Liberti
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, 32610, USA.
authors.forename: Moyi
authors.initials: M
authors.lastname: Li
authors.affiliation: Environmental Biotechnology Research Centre, 125 Gwahak-Ro, Yuseong-Gu, Daejeon, 305-806, South Korea.
authors.forename: Young-Tae
authors.initials: YT
authors.lastname: Kim
authors.affiliation: University of Maryland Medical Center, 22 S. Greene Street, Baltimore, MD, 21201, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Hutchens
authors.affiliation: Department of Plant Pathology, University of Florida, Gainesville, FL, 32611-0680, USA.
authors.forename: Ron
authors.initials: R
authors.lastname: Wilson
authors.affiliation: Department of Plant Pathology, University of Florida, Gainesville, FL, 32611-0680, USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Rollins
mesh_terms: D001203:Ascomycota / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D003001:Cloning, Molecular; D006867:Hydrolases / Q000235:genetics*; D009154:Mutation; D019815:Oxalic Acid / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D014774:Virulence
chemical_list: D012333:RNA, Messenger; D019815:Oxalic Acid; D006867:Hydrolases; C054172:oxaloacetase
keywords: Sclerotinia; necrotroph; oxalate; oxalic acid; pathogenesis; phytopathogen; virulence