Data_Sheet_1_The immunity priming effect of the Arabidopsis phyllosphere resident yeast Protomyces arabidopsidicola strain C29.PDF

The phyllosphere is a complex habitat for diverse microbial communities. Under natural conditions, multiple interactions occur between host plants and phyllosphere resident microbes, such as bacteria, oomycetes, and fungi. Our understanding of plant associated yeasts and yeast-like fungi lags behind other classes of plant-associated microbes, largely due to a lack of yeasts associated with the model plant Arabidopsis, which could be used in experimental model systems. The yeast-like fungal species Protomyces arabidopsidicola was previously isolated from the phyllosphere of healthy wild-growing Arabidopsis, identified, and characterized. Here we explore the interaction of P. arabidopsidicola with Arabidopsis and found P. arabidopsidicola strain C29 was not pathogenic on Arabidopsis, but was able to survive in its phyllosphere environment both in controlled environment chambers in the lab and under natural field conditions. Most importantly, P. arabidopsidicola exhibited an immune priming effect on Arabidopsis, which showed enhanced disease resistance when subsequently infected with the fungal pathogen Botrytis cinerea. Activation of the mitogen-activated protein kinases (MAPK), camalexin, salicylic acid, and jasmonic acid signaling pathways, but not the auxin-signaling pathway, was associated with this priming effect, as evidenced by MAPK3/MAPK6 activation and defense marker expression. These findings demonstrate Arabidopsis immune defense priming by the naturally occurring phyllosphere resident yeast species, P. arabidopsidicola, and contribute to establishing a new interaction system for probing the genetics of Arabidopsis immunity induced by resident yeast-like fungi.

叶围（phyllosphere）是承载多样微生物群落的复杂生境。自然条件下，宿主植物与定殖于叶围的细菌、卵菌及真菌等微生物之间存在多重相互作用。目前学界对植物相关酵母菌及类酵母菌的研究认知，滞后于其他类群的植物关联微生物，这在很大程度上源于缺乏可用于实验模型系统的、与模式植物拟南芥（Arabidopsis）共生的酵母菌资源。此前已有研究从健康野生拟南芥的叶围中分离得到类酵母菌菌株拟南芥生芽殖酵母（Protomyces arabidopsidicola，P. arabidopsidicola）并完成鉴定与特征分析。本研究探究了P. arabidopsidicola与拟南芥的相互作用，发现菌株C29对拟南芥无致病性，但可在实验室可控环境培养箱及自然田间条件下的叶围环境中稳定存活。尤为关键的是，P. arabidopsidicola对拟南芥具有免疫激发效应：经其预处理的植株在后续感染真菌病原菌灰葡萄孢（Botrytis cinerea）时，抗病性显著提升。该激发效应与丝裂原活化蛋白激酶（mitogen-activated protein kinases，MAPK）、卡马霉素（camalexin）、水杨酸（salicylic acid）及茉莉酸（jasmonic acid）信号通路的激活密切相关，但不涉及生长素信号通路，这一结论可通过MAPK3/MAPK6的激活及防御标记基因的表达水平得到验证。本研究证实了天然叶围定殖类酵母菌P. arabidopsidicola可激发拟南芥的免疫防御反应，同时为探究定殖类酵母菌诱导的拟南芥免疫遗传学机制建立了全新的互作研究体系。