Abstract
SummaryAuxin plays a fundamental role in plant growth and development, and also influences plant defence against various pathogens. Previous studies have examined the different roles of the auxin pathway during infection by biotrophic bacteria and necrotrophic fungi. We now show that the auxin signalling pathway was markedly down‐regulated following infection of rice by Rice black streaked dwarf virus (RBSDV), a dsRNA virus. Repression of the auxin receptor TIR1 by a mutant overexpressing miR393 increased rice susceptibility to RBSDV. Mutants overexpressing the auxin signalling repressors OsIAA20 and OsIAA31 were also more susceptible to RBSDV. The induction of jasmonic acid (JA) pathway genes in response to RBSDV was supressed in auxin signalling mutants, suggesting that activation of the JA pathway may be part of the auxin signalling‐mediated rice defence against RBSDV. More importantly, our results also revealed that OsRboh‐mediated reactive oxygen species levels played important roles in this defence. The results offer novel insights into the regulatory mechanisms of auxin signalling in the rice–RBSDV interaction.
Highlights
Auxins play key roles in almost every aspect of plant growth and development, regulating many processes by changes in their concentration
Rice plants were severely dwarfed after Rice black streaked dwarf virus (RBSDV) infection (Fig. 1A) and the effect of RBSDV infection on the auxin pathway was investigated in rice
The OsGH3 family genes are reported to reduce auxin content by catalysing the conjugation of IAA to amino acids and we found that the expression of OsGH3.2 and OsGH3.8 was markedly increased in our RBSDV-infected plants
Summary
Auxins play key roles in almost every aspect of plant growth and development, regulating many processes by changes in their concentration. Besides its role in plant development, recent studies have demonstrated that auxin is involved in plant defence (Fu and Wang, 2011; Vidhyasekaran, 2015). Repressing auxin signalling by the overexpression of miR393 increased resistance of Arabidopsis to the bacterial pathogen Pseudomonas syringae (Navarro et al, 2006). Auxin signalling was believed to antagonize the salicylic acid (SA)-mediated disease resistance pathway in response to bacterial invasion (Wang et al, 2007). Auxin signalling plays multiple roles in plant defence against necrotrophic fungal pathogens (Llorente et al, 2008; Qi et al, 2012). Disruption of the auxin signalling pathway increased susceptibility to Alternaria brassicicola, possibly because the induction of the jasmonic acid (JA) pathway related genes was suppressed (Qi et al, 2012). Auxin signalling and transport increased the susceptibility of Arabidopsis to Fusarium oxysporum (Kidd et al, 2011). The effect of the auxin pathway on plant defence is complicated, depending on the pathogen and host
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