Fernández I, Merlos M, López-Ráez J A, Martínez-Medina A, Ferrol N, Azcón C, Bonfante P, Flors V, Pozo M J
Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín (CSIC), Granada, Spain.
J Chem Ecol. 2014 Jul;40(7):791-803. doi: 10.1007/s10886-014-0473-6. Epub 2014 Jul 6.
Arbuscular mycorrhizal (AM) symbioses are mutualistic associations between soil fungi and most vascular plants. Modulation of the hormonal and transcriptional profiles, including changes related to defense signalling, has been reported in many host plants during AM symbioses. These changes have been often related to the improved stress tolerance common in mycorrhizal plants. However, results on the alterations in phytohormones content and their role on the symbiosis are controversial. Here, an integrative analysis of the response of phylogenetically diverse plants (i.e., tomato, soybean, and maize) to two mycorrhizal fungi -Funneliformis mosseae and Rhizophagus irregularis- was performed. The analysis of the defense-related hormones salicylic acid, abscisic acid, and jasmonates, and the expression of marker genes of the pathways they regulate, revealed significant changes in the roots of mycorrhizal plants. These changes depended on both the plant and the AM fungus (AMF) involved. However, general trends can be identified: roots associated with the most effective colonizer R. irregularis showed fewer changes in these defense-related traits, while the colonization by F. mosseae led to significant modifications in all plants tested. The up-regulation of the jasmonate pathway by F. mosseae was found to be highly conserved among the different plant species, suggesting an important role of jasmonates during this AM interaction. Our study evidences a strong influence of the AMF genotype on the modulation of host defense signalling, and offers hints on the role of these changes in the symbiosis.
丛枝菌根（AM）共生是土壤真菌与大多数维管植物之间的互利共生关系。在许多寄主植物的AM共生过程中，已报道了激素和转录谱的调节，包括与防御信号相关的变化。这些变化通常与菌根植物中常见的胁迫耐受性提高有关。然而，关于植物激素含量的变化及其在共生中的作用的结果存在争议。在此，对系统发育上不同的植物（即番茄、大豆和玉米）对两种菌根真菌——摩西斗管囊霉和不规则球囊霉——的反应进行了综合分析。对与防御相关的激素水杨酸、脱落酸和茉莉酸以及它们所调节途径的标记基因表达的分析表明，菌根植物的根中发生了显著变化。这些变化取决于所涉及的植物和AM真菌（AMF）。然而，可以确定一般趋势：与最有效的定殖者不规则球囊霉相关的根在这些与防御相关的性状上变化较少，而摩西斗管囊霉的定殖导致所有测试植物发生显著改变。发现摩西斗管囊霉对茉莉酸途径的上调在不同植物物种中高度保守，这表明茉莉酸在这种AM相互作用中起重要作用。我们的研究证明了AMF基因型对寄主防御信号调节的强烈影响，并为这些变化在共生中的作用提供了线索。
