Liao Dehua, Chen Xiao, Chen Aiqun, Wang Huimin, Liu Jianjian, Liu Junli, Gu Mian, Sun Shubin, Xu Guohua
State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, 210095, China These authors contributed equally to this work.
State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, 210095, China
Plant Cell Physiol. 2015 Apr;56(4):674-87. doi: 10.1093/pcp/pcu212. Epub 2014 Dec 21.
In plants, the GH3 gene family is widely considered to be involved in a broad range of plant physiological processes, through modulation of hormonal homeostasis. Multiple GH3 genes have been functionally characterized in several plant species; however, to date, limited works to study the GH3 genes in tomato have been reported. Here, we characterize the expression and regulatory profiles of six tomato GH3 genes, SlGH3.2, SlGH3.3, SlGH3.4, SlGH3.7, SlGH3.9 and SlGH3.15, in response to different phytohormone applications and arbuscular mycorrhizal (AM) fungal colonization. All six GH3 genes showed inducible responses to external IAA, and three members were significantly up-regulated in response to AM symbiosis. In particular, SlGH3.4, the transcripts of which were barely detectable under normal growth conditions, was strongly activated in the IAA-treated and AM fungal-colonized roots. A comparison of the SlGH3.4 expression in wild-type plants and M161, a mutant with a defect in AM symbiosis, confirmed that SlGH3.4 expression is highly correlated to mycorrhizal colonization. Histochemical staining demonstrated that a 2,258 bp SlGH3.4 promoter fragment could drive β-glucuronidase (GUS) expression strongly in root tips, steles and cortical cells of IAA-treated roots, but predominantly in the fungal-colonized cells of mycorrhizal roots. A truncated 654 bp promoter failed to direct GUS expression in IAA-treated roots, but maintained the symbiosis-induced activity in mycorrhizal roots. In summary, our results suggest that a mycorrhizal signaling pathway that is at least partially independent of the auxin signaling pathway has evolved for the co-regulation of the auxin- and mycorrhiza-activated GH3 genes in plants.
在植物中，GH3基因家族被广泛认为通过调节激素稳态参与多种植物生理过程。多个GH3基因已在几种植物物种中进行了功能表征；然而，迄今为止，关于番茄中GH3基因的研究报道有限。在此，我们表征了六个番茄GH3基因SlGH3.2、SlGH3.3、SlGH3.4、SlGH3.7、SlGH3.9和SlGH3.15在响应不同植物激素处理和丛枝菌根（AM）真菌定殖时的表达和调控模式。所有六个GH3基因均对外源吲哚-3-乙酸（IAA）表现出诱导反应，并且三个成员在响应AM共生时显著上调。特别是，SlGH3.4在正常生长条件下几乎检测不到其转录本，但在IAA处理和AM真菌定殖的根中被强烈激活。比较野生型植物和AM共生缺陷突变体M161中SlGH3.4的表达，证实SlGH3.4的表达与菌根定殖高度相关。组织化学染色表明，一个2258 bp的SlGH3.4启动子片段可在IAA处理根的根尖、中柱和皮层细胞中强烈驱动β-葡萄糖醛酸酶（GUS）表达，但主要在菌根根的真菌定殖细胞中表达。一个截短的654 bp启动子在IAA处理的根中未能指导GUS表达，但在菌根根中保持共生诱导活性。总之，我们的结果表明，植物中已经进化出一种至少部分独立于生长素信号通路的菌根信号通路，用于共同调节生长素和菌根激活的GH3基因。
