Division of Plant Biology, Bose Institute, P1/12 C. I. T. Scheme VIIM, Kolkata 700054, West Bengal, India.
Plant Physiol Biochem. 2013 Sep;70:43-51. doi: 10.1016/j.plaphy.2013.04.025. Epub 2013 May 21.
This work addresses the changes in the phytohormonal signature in the recognition of the necrotrophic fungal pathogen Alternaria brassicicola by susceptible Brassica juncea and resistant Sinapis alba. Although B. juncea, S. alba and Arabidopsis all belong to the same family, Brassicaceae, the phytohormonal response of susceptible B. juncea towards this pathogen is unique because the latter two species express non-host resistance. The differential expression of the PR1 gene and the increased level of salicylic acid (SA) indicated that an SA-mediated biotrophic mode of defence response was triggered in B. juncea upon challenge with the pathogen. Compared to B. juncea, resistant S. alba initiated enhanced abscisic acid (ABA) and jasmonic acid (JA) responses following challenge with this pathogen, as revealed by monitoring the expression of ABA-related genes along with the concentration of ABA and JA. Furthermore, these results were verified by the exogenous application of ABA on B. juncea leaves prior to challenge with A. brassicicola, which resulted in a delayed disease progression, followed by the inhibition of the pathogen-mediated increase in SA response and enhanced JA levels. Therefore, it seems that A. brassicicola is steering the defence response towards a biotrophic mode by mounting an SA response in susceptible B. juncea, whereas the enhanced ABA response of S. alba not only counteracts the SA response but also restores the necrotrophic mode of resistance by enhancing JA biosynthesis.
这项工作研究了在识别坏死真菌病原体交替单胞菌（Alternaria brassicicola）时，敏感植物芥菜（Brassica juncea）和抗性荠（Sinapis alba）中植物激素特征的变化。尽管芥菜、荠和拟南芥都属于同一科，即十字花科，但敏感芥菜对这种病原体的植物激素反应是独特的，因为后两种植物表现出非寄主抗性。PR1 基因的差异表达和水杨酸（SA）水平的增加表明，在受到病原体攻击时，芥菜中触发了一种由 SA 介导的生物亲和防御反应。与芥菜相比，抗性荠在受到这种病原体的挑战后，会引发增强的脱落酸（ABA）和茉莉酸（JA）反应，这可以通过监测与 ABA 和 JA 相关的基因表达以及 ABA 和 JA 的浓度来揭示。此外，通过在受到交替单胞菌攻击之前将外源 ABA 应用于芥菜叶片，验证了这些结果，这导致疾病进展延迟，随后抑制了病原体介导的 SA 反应增加和 JA 水平增强。因此，交替单胞菌似乎通过在敏感芥菜中引发 SA 反应来引导防御反应向生物亲和模式发展，而荠增强的 ABA 反应不仅抵消了 SA 反应，还通过增强 JA 生物合成恢复了坏死抗性模式。
