Arbuscular mycorrhizas (AMs) are divided into two types according to morphology: Arum- and Paris-type AMs. Gibberellins (GAs) mainly inhibit the establishment of Arum-type AM symbiosis in most model plants, whereas the effects of GAs on Paris-type AM symbiosis are unclear. To provide insight into the mechanism underlying this type of symbiosis, the roles of GAs were investigated in Eustoma grandiflorum when used as the host plant for Paris-type AM establishment. Eustoma grandiflorum seedlings were inoculated with the model AM fungus, Rhizophagus irregularis, and the effects of GA and the GA biosynthesis inhibitor uniconazole-P on the symbiosis were quantitatively evaluated. Exogenous GA significantly increased hyphopodium formation at the epidermis, thus leading to the promotion of fungal colonization and arbuscule formation in the root cortex. By contrast, the suppression of GA biosynthesis and signaling attenuated fungal entry to E. grandiflorum roots. Moreover, the exudates from GA-treated roots strongly induced the hyphal branching of R. irregularis. Our results show that GA has an contrasting effect on Paris-type AM symbiosis in E. grandiflorum compared with Arum-type AM symbiosis. This finding could be explained by the differential regulation of the early colonization stage, where fungal hyphae make contact with and penetrate the epidermis.

中文翻译：

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赤霉素促进桔梗巴黎型丛枝菌根共生期间的真菌进入和定居。

根据形态将丛枝菌根（AM）分为两种：Arum型和Paris型AM。赤霉素（GAs）在大多数模型植物中主要抑制Arum型AM共生的建立，而GA对Paris型AM共生的影响尚不清楚。为了提供对这种共生基础的机制的见解，在将洋桔梗用作巴黎型AM建立的寄主植物时，对其进行了研究。用模型AM真菌，不规则根瘤菌接种桔梗幼苗，并定量评估GA和GA生物合成抑制剂烯康唑-P对共生的影响。外源GA显着增加了表皮上的次球体形成，从而促进了根皮层中真菌定植和丛枝的形成。相比之下，GA生物合成的抑制和信号传导减弱了真菌进入大肠埃希氏菌根的能力。而且，来自经GA处理的根的渗出液强烈诱导不规则红杆菌的菌丝分支。我们的结果表明，与阿鲁姆型AM共生相比，GA对大肠埃希菌的巴黎型AM共生具有相反的作用。这一发现可以通过早期定居阶段的差异调节来解释，在该阶段，真菌菌丝与表皮接触并穿透表皮。