Vitamin B Mediated Priming of Disease Resistance and Defense Responses to Tobacco Mosaic Virus in Capsicum annuum L. Plants

Abstract

Thiamin (B1) and riboflavin (B2) can act as activators and priming factors of defense mechanisms for Tobacco Mosaic Virus (TMV) infection in Capsicum annuum plants. Effect of exogenous application of each vitamin on C. annuum leaves was demonstrated to induce defense responses and systemic resistance against TMV in the untreated parts of the plant. A range of concentrations was used of both vitamins. 70% of inhibition of TMV for thiamin and 64.1% for riboflavin were achieved, when applied just before virus inoculation. The induction of disease resistance and reduction of virus infectivity in C. annuum leaves were determined by indirect ELISA and local lesion host plant assay. The synergetic effect of both vitamins on TMV disease reduction was studied. To investigate the defensive enzymes responsible for the induction of resistance, the levels of Phenylalanine ammonia-lyase (PAL), Polyphenol Oxidase (PPO), and Peroxidase (POD) were examined by specific enzyme assay for each one, and the accumulation of the enzymes was detected 0 to 20 days after treating with the vitamins. Also, the up-regulation and expression of the defense genes POD, PPO, PAL, and some of the pathogenesis related proteins, PR4, PR9, and PR10 were studied by reverse transcriptase polymerase chain reaction (RT-PCR). Application of vitamins B1, and B2 significantly increased the activities of some of the pathogenesis related enzymes, and genes. The possible correlation between timing of application of elicitors and expression of defensive genes was also studied.