Waller Frank, Mukherjee Krishnendu, Deshmukh Sachin D, Achatz Beate, Sharma Monica, Schäfer Patrick, Kogel Karl-Heinz
Research Center for BioSystems, Land Use and Nutrition, Institute of Phytopathology and Applied Zoology, Justus-Liebig-University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany.
J Plant Physiol. 2008 Jan;165(1):60-70. doi: 10.1016/j.jplph.2007.05.017. Epub 2007 Nov 26.
Piriformospora indica is a fungus of the order Sebacinales (Basidiomycota) infesting roots of mono- and dicotyledonous plants. Endophytic fungal colonization leads to enhanced plant growth while host cell death is required for proliferation in differentiated root tissue to form a mutualistic interaction. Colonization of barley roots by P. indica and related Sebacina vermifera strains also leads to systemic resistance against the leaf pathogenic fungus Blumeria graminis f.sp. hordei due to a yet unknown mechanism of induced resistance. In order to elucidate plant response pathways governed by these root endophytes, we analyzed gene expression in barley plants exhibiting an established symbiosis with P. indica 3 weeks after inoculation. P. indica-colonized roots showed no induction of defence-related genes, while other genes showed a differential regulation pattern indicating a faster P. indica-dependent root development. Gene expression analysis of leaves detected only few systemically induced mRNAs. Among differentially regulated transcripts, we characterized the pathogenesis-related gene HvPr17b and the molecular chaperone HvHsp70 in more detail. HvPr17b shows similarity with TaWCI5, a wheat gene inducible by chemical resistance inducers and salicylate, and was previously proven to exhibit antifungal activity against B. graminis. HvHsp70 is the first gene found to systemically indicate root colonization with endophytic fungi of the order Sebacinales. Both genes are discussed as markers for endophytic colonization and resulting systemic responses.
印度梨形孢是一种座囊菌目（担子菌门）真菌，寄生于单子叶和双子叶植物的根部。内生真菌定殖会促进植物生长，而在分化的根组织中增殖形成共生相互作用则需要宿主细胞死亡。印度梨形孢和相关的蚯蚓状座囊菌菌株定殖大麦根也会通过一种未知的诱导抗性机制，引发对叶部致病真菌大麦白粉菌的系统抗性。为了阐明这些根内生菌调控的植物反应途径，我们分析了接种3周后与印度梨形孢建立共生关系的大麦植株中的基因表达。被印度梨形孢定殖的根未诱导防御相关基因，而其他基因呈现出差异调控模式，表明印度梨形孢依赖的根发育更快。叶片的基因表达分析仅检测到少数系统诱导的mRNA。在差异调控的转录本中，我们更详细地鉴定了病程相关基因HvPr17b和分子伴侣HvHsp70。HvPr17b与TaWCI5相似，TaWCI5是一个受化学抗性诱导剂和水杨酸诱导的小麦基因，先前已证明其对大麦白粉菌具有抗真菌活性。HvHsp70是首个被发现可系统指示被座囊菌目内生真菌根定殖的基因。这两个基因都被作为内生菌定殖及由此产生的系统反应的标记物进行讨论。
