Degradation of oxalic acid by the mycoparasite Coniothyrium minitans plays an important role in interacting with Sclerotinia sclerotiorum.
Coniothyrium minitans (Cm) is a mycoparasite of the phytopathogenic fungus Sclerotinia sclerotiorum (Ss). Ss produces a virulence factor oxalic acid (OA) which is toxic to plants and also to Cm, and Cm detoxifies OA by degradation. In this study, two oxalate decarboxylase genes, Cmoxdc1 and Cmoxdc2, were cloned from Cm strain Chy-1. OA and low pH induced expression of Cmoxdc1, but not Cmoxdc2. Cmoxdc1 was partially responsible for OA degradation, whereas Cmoxdc2 had no effect on OA degradation. Disruption of Cmoxdc1 in Cm reduced its ability to infect Ss in dual cultures where OA accumulated. Compared with Chy-1, the Cmoxdc1-disrupted mutants had reduced expression levels of two mycoparasitism-related genes chitinase (Cmch1) and β-1,3-glucanase (Cmg1), and had no detectable activity of extracellular proteases in the presence of OA. On the other hand, the cultural filtrates of the Cmoxdc1-disrupted mutants in OA-amended media showed enhanced antifungal activity, possibly because of increased production of antifungal substances under acidic pH condition resulted from reduced Cmoxdc1-mediated OA degradation. This study provides direct genetic evidence of OA degradation regulating mycoparasitism and antibiosis of Cm against Ss, and sheds light on the sophisticated strategies of Cm in interacting with metabolically active mycelia and dormant sclerotia of Ss.
State Key Laboratory of Agricultural Microbiology, Key Laboratory of Plant Pathology of Hubei Province, Huazhong Agricultural University, Wuhan, China.
Li-Mei
LM
Zeng
Jing
J
Zhang
Yong-Chao
YC
Han
Long
L
Yang
Ming-de
MD
Wu
Dao-Hong
DH
Jiang
Weidong
W
Chen
Guo-Qing
GQ
Li
D000898:Antibiosis; D000935:Antifungal Agents / Q000378:metabolism; D002262:Carboxy-Lyases / Q000235:genetics* / Q000378:metabolism; D002688:Chitinases / Q000235:genetics* / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D043326:Glucan 1,3-beta-Glucosidase; D054884:Host-Pathogen Interactions; D019815:Oxalic Acid / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D004718:Saccharomycetales / Q000201:enzymology / Q000235:genetics*; D013379:Substrate Specificity; D037521:Virulence Factors / Q000378:metabolism*
D000935:Antifungal Agents; D005656:Fungal Proteins; D011994:Recombinant Proteins; D037521:Virulence Factors; D019815:Oxalic Acid; D002688:Chitinases; D043326:Glucan 1,3-beta-Glucosidase; D002262:Carboxy-Lyases; C021915:oxalate decarboxylase