Title

Fungal oxalate decarboxylase Activity Contributes to Sclerotinia sclerotiorum Early Infection by Affecting Both Compound Appressoria Development and Function

Department

Chemistry & Biochemistry

Document Type

Article

Publication Date

4-15-2015

Abstract

Sclerotinia sclerotiorum pathogenesis requires the accumulation of high levels of oxalic acid (OA). To better understand the factors affecting OA accumulation, two putative oxalate decarboxylase (OxDC) genes (Ss-odc1 and Ss-odc2) were characterized. Ss-odc1 transcripts exhibited significant accumulation in vegetative hyphae, apothecia, early stages of compound appressorium development and during plant colonization. Ss-odc2 transcripts, in contrast, accumulated significantly only during mid to late stages of compound appressorium development. Neither gene was induced by low pH or exogenous OA in vegetative hyphae. A loss-of-function mutant for Ss-odc1 (Δss-odc1) showed wild-type growth, morphogenesis and virulence, and was not characterized further. Δss-odc2 mutants hyperaccumulated OA in vitro, were less efficient at compound appressorium differentiation and exhibited a virulence defect which could be fully bypassed by wounding the host plant prior to inoculation. All Δss-odc2 phenotypes were restored to the wild-type by ectopic complementation. An S. sclerotiorum strain overexpressing Ss-odc2 exhibited strong OxDC, but no oxalate oxidase activity. Increasing inoculum nutrient levels increased compound appressorium development, but not penetration efficiency, of Δss-odc2 mutants. Together, these results demonstrate differing roles for S. sclerotiorum OxDCs, with Odc2 playing a significant role in host infection related to compound appressorium formation and function.

Journal

Molecular Plant Pathology

Journal ISSN

1364-3703

Volume

16

Issue

8

First Page

825

Last Page

836

Digital Object Identifier (DOI)

10.1111/mpp.12239