Assessing functional role of three water deficit stress-induced genes in nonhost disease resistance using virus-induced gene silencing in Nicotiana benthamiana

Nonhost disease resistance is the most common form of disease resistance exhibited by all plants and to date this phenomenon is not yet completely understood. Understanding the mechanisms behind nonhost resistance may facilitate engineering crop plants with durable resistance. Our previous studies identified putative roles for three genes flavonol-3-O-glucosyl transferase (F3OGT), an alcohol dehydrogenase (ADH) and trans caffeoyl coA-3-O methyl transferase (CcoAOMT) in water deficit stress tolerance. Preliminary information from our earlier study also suggested that Arabidopsis null mutants for these genes exhibited altered levels of tolerance to bacterial pathogens. In this manuscript we document more evidences to show the relevance of these genes in nonhost resistance using Nicotiana benthamiana. By using virus-induced gene silencing (VIGS), we independently downregulated these three genes and analyzed the response of gene silenced plants to bacterial pathogens. Our results showed that F3OGT, a gene implicated in anthocyanin biosynthesis, silenced plants compromised resistance against a nonhost pathogen. Based on this and previous results, we propose that anthocyanin might play a role in regulating plant defense against bacterial pathogens. Response of ADH or CcoAOMT gene silenced plants to bacterial nonhost pathogens was similar to wild-type. However, CcoAOMT gene downregulated plants were slightly more susceptibility to a host pathogen.