Degradation of oxalic acid by the mycoparasite Coniothyrium minitans plays an important role in interacting with Sclerotinia sclerotiorum

Abstract

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.

The control of sclerotinia stem rot on oilseed rape (Brassica napus): current practices and future opportunities

“…The role of oxalic acid in the mycoparasitism of C. minitans on S. sclerotiorum was further confirmed by studying oxalate decarboxylase deficient mutants of C. minitans , which had lost the ability to break down oxalic acid. When co‐incubated with S. sclerotiorum the Cmoxdc1 mutant had a reduced ability to infect the mycelia of S. sclerotiorum compared to wildtype C. minitans (Zeng et al ., ). In addition to its ability to break down oxalic acid, C. minitans is also proposed to secrete antifungal compounds.…”

The oxalyl‐CoA synthetase‐regulated oxalate and its distinct effects on resistance to bacterial blight and aluminium toxicity in rice

“…Oxalate is an important virulence determinant for some pathogenic microorganisms such as Sclerotinia sclerotiorum (Zeng et al 2014). There have been reports that when OCS was mutated in Medicago the mutants were more sensitive to S. sclerotiorum (Foster et al 2016).…”

Multiple criteria-based screening of Trichoderma isolates for biological control of Botrytis cinerea on tomato

“…The culture filtrate was prepared by filtering (Zhang et al, 2014) and amended in PDA at the volume ratio of 10% (v/v). PDA amended with the same volume of sterilized water was used as control.…”

“…A 1-to 2-mm cross section of the root piece and the stem piece were transversely cut with a sharp razor blade from a tap root at 1 cm below and 1 cm above the substrate surface, respectively. The root piece or the stem piece were then surface-sterilized in 70% ethanol (v/v) for 1 min, then in 5% sodium hypochlorite (v/v) for 5 min, again in a 70% ethanol for 30 s, and finally rinsed in sterile water for three times at three minutes each time (Zhang et al, 2014). They were placed in Petri dishes containing PDA amended with lactic acid for inhibition of bacterial growth, one root piece or stem piece per dish.…”