Jasmonic acid and methyl jasmonate modulate growth, photosynthetic activity and expression of photosystem II subunit genes in Brassica oleracea L

The effects of jasmonic acid (JA) and methyl jasmonate (Me-JA) on photosynthetic efficiency and expression of some photosystem (PSII) related in different cultivars of Brassica oleracea L. (var. italica, capitata, and botrytis) were investigated. Plants raised from seeds subjected to a pre-sowing soaking treatment of varying concentrations of JA and Me-JA showed enhanced photosynthetic efficiency in terms of qP and chlorophyll fluorescence. Maximum quantum efficiency of PSII (Fv/Fm) was increased over that in the control seedlings. This enhancement was more pronounced in the Me-JA-treated seedlings compared to that in JA-treated ones. The expression of PSII genes was differentially regulated among the three varieties of B. oleracea. The gene PsbI up-upregulated in var. botrytis after treatment of JA and Me-JA, whereas PsbL up-regulated in capitata and botrytis after supplementation of JA. The gene PsbM showed many fold enhancements in these expressions in italica and botrytis after treatment with JA. However, the expression of the gene PsbM increased by both JA and Me-JA treatments. PsbTc(p) and PsbTc(n) were also found to be differentially expressed which revealed specificity with the variety chosen as well as JA or Me-JA treatments. The RuBP carboxylase activity remained unaffected by either JA or Me-JA supplementation in all three varieties of B. oleracea L. The data suggest that exogenous application of JA and Me-JA to seeds before germination could influence the assembly, stability, and repair of PS II in the three varieties of B. oleracea examined. Furthermore, this improvement in the PS II machinery enhanced the photosynthetic efficiency of the system and improved the photosynthetic productivity in terms of saccharides accumulation.