Debabrata Sircar
Indian Institute of Technology Roorkee, India
Title: Functional genomic analysis of inducible defense responses to Venturia inaquelis infection in scab-resistant apple genotypes
Biography
Biography: Debabrata Sircar
Abstract
Apple is the main deciduous fruit crop in the India and worldwide, consumed for its delicious test and health-protective constituents. However, dramatic losses in fruits and trees are caused by the apple scab fungus Venturia inaquelis. To combat this disease, apple forms antifungal metabolites, so-called phytoalexins. Although apple has high economic value, metabolism of these pathogen-inducible defence compounds is poorly understood. This deficit prevents biotechnological exploitation of phytoalexin metabolism for enhancement of disease resistance. The present study reports the differetial accumulation of two special class of phytoalexins (biphenyl and dibenzofurans) in the scab-resistant apple cultivar. GC-MS based targated metabolomics analyses revealed the accumulation six major phytoalexins upon scab infection. Using a subtracted complementary DNA (cDNA) library and sequence information from Genome Database of Rosaceae, a cDNA encoding the o-methyltransferase (MdOMT1) enzymes was isolated from scab-infected apple plants. MdOMT1 utilyzed 3,5-dihydroxybiphenyl as a preffered substrate, converting it to 3-hydroxy-5-methoxybiphenyl, the precursor of noraucuparin biosynthesis. Methylation of 3,5-dihydroxybiphenyl proceeds only on one hydroxyl group. Expression of SaOMT1 was transiently induced in apple plants upon scab-infection. High expression level of MdOMT1 precedes the accumulation of noraucuparin. SaOMT1 was N- and C-terminally fused with the modified yellow fluorescent protein (YFP) and the fluorescent reporter fusions products were localized to the cytoplasm of the leaf epidermis cells of Nicotiana benthamiana. Collectively, our results demonstrated that phytoalexin biosynthesis plays crucial role in detrmining inducible defense responses to Venturia inaquelis infection in scab-resistant apple cultivars.