Understanding the role of uncharacterized and hypothetical pathogenicity genes of Colletotrichum orbiculare to oxidative stress and phenolics of cucumber plant in anthracnose development
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Date
2019-12
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NISCAIR-CSIR, India
Abstract
Uncharacterized and hypothetical pathogenicity genes of Colletotrichum orbiculare inciting anthracnose of cucumber are poorly annotated but could be potential antifungal targets in anthracnose control. Hence, to associate them with specific functions in fungal–host interactions for exploitation in anthracnose control, their responses to reactive oxygen species produced due to oxidative burst and constitutive or induced phenolics, the earliest known defence mechanisms of host plants were assessed. Among commercially available related phenolic compounds, at the lowest concentration of 1 mM, ferulic and chlorogenic acids were less toxic to the pathogen. Among the phenolics, a less significant expression of superoxide dismutase coupled with a strong expression of catalase in ferulic acid greater than that in menadione and hydrogen peroxide, respectively indicated its oxidative effect through generation of radicles similar to that of hydrogen peroxide. However, lack of expression of beta-ketoadipate pathway genes in response to the phenolic acids indicated the role of other phenol metabolizing genes of the pathogen. In planta expression followed by constitutive expression of uncharacterized and hypothetical pathogenicity genes of C. orbiculare in a minimal medium indicated that 6 of the genes are not redundant and may function under stress conditions. Among the genes, significant expression of ENH87556 in menadione (1.3-fold) together with a weak expression in hydrogen peroxide in relation to untreated control indicated its role in oxidative stress generated due to the superoxide radical of menadione. Additionally, a strong expression (3.8-fold) of the gene in ferulic acid greater than that of either control, minimal medium or minimal medium with leaf extract indicated its role in phenol metabolism. Thus, the gene could be a potential molecular target for anthracnose control upon validation by functional analysis.
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Shanmugam V, Veena KH, Jain Shekhar, Aggarwal Rashmi, Ilakkiyaselvan G. Volatile, nonvolatile composition and biological activities of Ageratum houstonianum Mill. against diamondback moth, Plutella xylostella (L.) and aphid, Aphis craccivora Koch. Indian Journal of Experimental Biology. 2019 Dec; 57(12): 908-915