Vitamin B6 biosynthetic genes expression and antioxidant enzyme properties in tomato against, Erwinia carotovora subsp. carotovora.

Vitamin B6 (VitB6) is an essential cofactor for >140 biochemical reactions. Also, VitB6 is a potent antioxidant and helps plants cope with both biotic and abiotic stress conditions. However, the role of VitB6 in plant disease resistance has yet to be confirmed using molecular biology approaches. Here, we analyzed the expression patterns of VitB6 biosynthetic genes, including the de novo (PDX1 [PDX1.2 and 1.3] and PDX2) and the salvage (SOS4) pathways during the response to Erwinia carotovora subsp. carotovora. By quantitative PCR, we found that the most significant upregulation in the transcript profile of PDX2, which showed a 9.2-fold increase in expression at 12 h post inoculation (hpi) compared to 24-48 hpi. We also detected significant upregulation of PDX1.2 and PDX1.3, which were 6.6- and 4.3-fold upregulated at 24 hpi compared to 12 hpi, while SOS4 showed only low-level expression. Also, at 24 hpi, a significant increase in superoxide dismutase, catalase, peroxidase, and polyphenol oxidase activities was observed in plants. Our findings confirm that the expression of de novo and salvage pathway genes is induced by E. carotovora and that this plays an important role in the regulation of defense response by modulating cellular antioxidant capacity.