Silicon improves the drought tolerance in pepper plants through the induction of secondary metabolites, GA biosynthesis pathway, and suppression of chlorophyll degradation.

ABSTRACT

Drought stress caused by the global climate considerably disturbs plant yield and growth. Here, we explored the putative roles of silicon in repressing drought mechanisms in pepper and the prominent involvement of secondary metabolites, GA pathway, and photosystem II. Our research revealed that the transcript level of the flavonoid biosynthesis-associated genes, including the PAL, 4-CL, CHS, FLS-1, F3H and DFR, progressively induced in the pepper leaves treated with silicon during the drought stress duration. Moreover, the phenolic and flavonoid compounds extensively induced in the pepper plants. Furthermore, the pepper plants markedly inhibited chlorophyll catabolic-allied genes, senescence-related marker gene, and the Rbohs gene. Silicon application also sustained the membrane stability, supported via fewer electrolyte leakage processes and minor, O2- H2O2 and MDA levels during drought. Apart from this, the pepper plants significantly induced the expression level of the photosystem II-related genes, osmoprotectants pathway-associated genes, and antioxidant defense genes. Moreover, the GA biosynthesis genes were prompted, while the ABA signaling and biosynthesis genes were suppressed in the silicon-supplemented plants. These consequences infer that the role of Si supplementation on enhancing drought tolerance could be elucidated through the activation of secondary metabolites, flavonoid biosynthesis, osmoprotectants, GA pathway, the efficiency of PSII, and the suppression of chlorophyll degradation. Our research outcomes unveil new and remarkable characteristics of silicon supplementation and offer a series of candidate targets for improving the tolerance of pepper plants to drought stress.