Nehls U, Béguiristain T, Ditengou F, Lapeyrie F, Martin F
Equipe de Microbiologie Forestière, Centre de Recherches de Nancy, Institut National de la Recherche Agronomique, Champenoux, France.
Planta. 1998 Dec;207(2):296-302. doi: 10.1007/s004250050486.
A full-length cDNA coding for a symbiosis-regulated transcript, EgHypar, was isolated by differential screening from a Eucalyptus globulus bicostata--Pisolithus tinctorius ectomycorrhiza. The sequence of this clone revealed a protein with an estimated molecular mass of 25.5 kDa that exhibited a high degree of homology (66%) with plant auxin-induced glutathione-S-transferases. Expression of the EgHypar gene in seedlings was confined largely in roots and it is drastically increased by ectomycorrhiza development. The concentration of EgHypar transcripts was similarly up-regulated in roots incubated in media supplemented with P. tinctorius cell-free extracts, indole-3-acetic acid, 2,4-dichlorophenoxyacetic acid or hypaphorine (tryptophan betaine), the major indolic compound secreted by P. tinctorius. The latter fungal alkaloid concomitantly induced a decrease in root hair elongation in eucalypt seedlings. Up-regulation of EgHypar expression by auxins and fungal metabolites suggests that this symbiosis-regulated gene could be involved in the morphological changes taking place in plants roots upon symbiosis development. To our knowledge, these results provide the first molecular evidence that gene expression of the host plant is altered by molecules produced by the ectomycorrhizal mycobiont.
通过差异筛选，从蓝桉双肋变种——彩色豆马勃外生菌根中分离出一个编码共生调节转录本EgHypar的全长cDNA。该克隆的序列显示出一种估计分子量为25.5 kDa的蛋白质，它与植物生长素诱导的谷胱甘肽-S-转移酶具有高度同源性（66%）。EgHypar基因在幼苗中的表达主要局限于根部，并且随着外生菌根的发育而急剧增加。在添加了彩色豆马勃无细胞提取物、吲哚-3-乙酸、2,4-二氯苯氧乙酸或Hypaphorine（色氨酸甜菜碱，彩色豆马勃分泌的主要吲哚类化合物）的培养基中培养的根中，EgHypar转录本的浓度同样上调。后一种真菌生物碱同时导致桉树苗根毛伸长减少。生长素和真菌代谢产物对EgHypar表达的上调表明，这个共生调节基因可能参与了共生发育过程中植物根部发生的形态变化。据我们所知，这些结果提供了第一个分子证据，即外生菌根菌根共生体产生的分子会改变宿主植物的基因表达。
