Nat N. V. Kav

Clubroot disease, caused by Plasmodiophora brassicae Woronin, results in severe yield losses in Brassica crops, including canola. Silicon (Si) mitigates several stresses and enhances plant resistance to phytopathogens. We investigated the effects of Si on clubroot disease symptoms in canola at two concentrations of Si, Si: soil in 1: 100 w/w (Si1.0) and Si: soil in 1:200 w/w (Si0.5) under greenhouse conditions. In addition, the effects of Si on P. brassicae ‐induced gene expression, endogenous levels of phytohormones and metabolites were studied using “omics” approaches. Si application reduced clubroot symptoms and improved plant growth parameters. Gene expression analysis revealed increased transcript‐level responses in Si1.0 compared to Si0.5 plants at 7‐, 14‐, and 21‐days post‐inoculation (dpi). Pathogen‐induced transcript‐level changes were affected by Si treatment, with genes related to antioxidant activity (e.g., POD , CAT ), phytohormone biosynthesis and signalling (e.g., PDF1.2 , NPR1, JAZ, IPT, TAA ), nitrogen metabolism (e.g., NRT, AAT ), and secondary metabolism (e.g., PAL , BCAT4 ) exhibiting differential expression. Endogenous levels of phytohormones (e.g., auxin, cytokinin), a majority of the amino acids and secondary metabolites (e.g., glucosinolates) were increased at 7 dpi, followed by a decrease at 14‐ and 21‐dpi due to Si‐treatment. Stress hormones such as abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA) also decreased at the later time points in Si0.5, and Si1.0 treated plants. Si appears to improve clubroot symptoms while enhancing plant growth and associated metabolic processes, including nitrogen metabolism and secondary metabolite biosynthesis.

C2H2-zinc finger (C2H2-ZF) genes are involved in various biological processes in plants including stress response; however, they lack characterization in Brassica napus. We identified 267 C2H2-ZF genes in B. napus and deciphered their physiological properties, subcellular localization, structure, synteny, and phylogeny and investigated the expression of 20 genes in response to different stresses and phytohormone treatments. The 267 genes were distributed on 19 chromosomes; phylogenetic analysis categorized them into five clades. They varied from 0.41 to 9.2 kb in length, had stress-responsive cis-acting elements in promoter regions, and their protein length varied from 9 to 1366 amino acids. About 42% of the genes had one exon, and 88% genes had orthologs in Arabidopsis thaliana. About 97% of the genes were located in nucleus and 3% in cytoplasmic organelles. qRT-PCR analysis showed a different expression pattern of these genes in response to biotic stresses ( Plasmodiophora brassicae and Sclerotinia sclerotiorum) and abiotic stresses (cold, drought, and salinity) and hormonal treatments. Differential expression of the same gene was observed under multiple stress conditions, and a few genes showed similar expression in response to more than one phytohormones. Our results suggest that the C2H2-ZF genes can be targeted for the improvement of stress tolerance in canola.