大麦Mlo近等基因系与叶枯病菌互作的细胞学研究

 本文对大麦品种Ingrid(Mlo)及Mlo基因功能丧失性突变的近等基因系(Ingrid mlo-3、Ingrid mlo-4和Ingrid mlo-5)与大麦叶枯病菌的互作进行了细胞学比较分析。结果发现,大麦mlo突变体mlo-3、mlo-4和mlo-5对叶枯病菌的抗病性显著增强,其抗病机制包括对病菌初侵染的乳突抗性和HR反应两个方面。Ingrid(Mlo)大麦的表皮细胞在受到病原菌侵染时,只有15%的有效乳突可成功抵抗病原菌对表皮细胞的侵染;而大麦mlo突变体mlo-3、mlo-4和mlo-5突变体大麦的有效乳突率则分别高达40%、38%和43%。随后,部分被病原菌成功侵入的寄主表皮细胞发生过敏性坏死,从而进一步抑制病原菌向相邻叶肉细胞的扩展。其中3个大麦mlo基因突变体平均67%的被侵染细胞坏死,而Ingrid仅为26%。因此,Mlo基因在调控大麦与不同病原菌互作中的作用是不同的。此外,本文发现该病原菌除气孔入侵外,还可直接穿透大麦表皮细胞;少量菌丝可以侵染进入叶肉细胞,甚至是活的叶肉细胞。

Cytological examination on interactions between Mlo near-isogenic lines of barley and their leaf blight pathogen,Alternaria tenuissima

Recessive alleles of the barley Mlo locus confer non-race specific broad-spectrum resistance against all the races of powdery mildew fungus, Blumeria graminis f. sp. hordei. To assay the biofunction of Mlo gene in regulation of plant defense response against different pathogens, the cytological events were examined in the interactions between Mlo near-isogenic lines of barley and their leaf blight pathogen, Alternaria tenuissima (Fr.) Wiltsh. The results showed that the Mlo loss-of-function mutants could enhance resistance to leaf blight pathogen in both papilla-associated resistance and hypersensitive response (HR). The effective papilla, which could arrest the pathogen to invade into barley epidermal cells, was 15% in the wild Mlo barley, Ingrid (Mlo);and, in contrast, 49%, 51%, 55% in Ingrid mlo-3, mlo-4, and mlo-5 mutants respectively. The HR of the invaded barley epidermal cells might limit the fungal further extension into adjacent mesophyll cells. The percentage of HR in epidermal cells was 64%-69% in mlo mutant lines but only 26% in wild Ingrid. These suggested that Mlo gene regulate the defense responses by different ways to various pathogens. In addition, it was found that the fungus could also penetrate the barley epidermal cells directly, and its hyphae could also invade and grow in barley mesophyll cells, even in the living ones.