Abstract
Biotic stresses negatively affect canola growth and production. Flea beetle damage and Sclerotinia sclerotiorum (S. sclerotiorum) infection are two of the worst biotic stresses for canola. Auxin Repressed Proteins (ARPs) responsive to several abiotic stresses have been reported. However, information about ARPs induced by Flea beetle damage and S. sclerotiorum infection, their roles in biotic stress tolerance are still lacking in canola. ESTs for an Auxin Repressed Protein 1 (BnARP1) were highly represented (expressed) in a Brassica napus subtractive library developed after leaf damage by the crucifer flea beetle (Phyllotreta cruciferae). Expression of this gene was under different developmental control in B. napus, and it was co-induced in B. napus by flea beetle feeding, S. sclerotiorum infection, drought and cold. A total of 25 BnARP genes were represented in different B. napus stress and development EST libraries and indicated larger, diversified families than known earlier. Dwarf phenotypes, primary root growth inhibition, lateral root enhancement, reduced sensitivity to 2, 4-D, and reduced PIN1 and LOX expression in transgenic Arabidopsis expression lines suggest that BnARP1 is an auxin repressor that prevents auxin transport and supports an interaction between the auxin and jasmonate signalling pathways. And the increased survival after S. sclerotiorum infection in transgenic over-expression Arabidopsis suggests that BnARP1 could play a role in S. sclerotiorum tolerance through connecting auxin and jasmonate signalling pathways.
Highlights
Plant resistance or tolerance to biotic stress consists of constitutive or induced defense mechanisms, and inducible defense is thought to be more durable than constitutive defense [1] [2]
ESTs for an Auxin Repressed Protein 1 (BnARP1) were highly represented in a Brassica napus subtractive library developed after leaf damage by the crucifer flea beetle (Phyllotreta cruciferae)
Expression of this gene was under different developmental control in B. napus, and it was co-induced in B. napus by flea beetle feeding, S. sclerotiorum infection, drought and cold
Summary
Plant resistance or tolerance to biotic stress consists of constitutive or induced defense mechanisms, and inducible defense is thought to be more durable than constitutive defense [1] [2]. It is clear that a plant’s response to challenge by insects and fungi is mediated by a network of cross-talking pathways and not by simple linear signal transduction cascades [2]. This network includes the jasmonic acid (JA), salicylic acid (SA), ethylene, abscisic acid (ABA) and auxin signalling pathways and presumably enables a coordinated, specific response. ABA-dependent signaling is well known for regulating abiotic stress-induced gene expression [11], and ABA antagonizes JA/ethylene-responsive defense gene expression and modulates disease resistance in Arabidopsis [12]
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