AUTHOR=Wang Kai , Auzane Agate , Overmyer Kirk 

TITLE=The immunity priming effect of the Arabidopsis phyllosphere resident yeast Protomyces arabidopsidicola strain C29

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.956018

DOI=10.3389/fmicb.2022.956018

ISSN=1664-302X

ABSTRACT=<p>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 <italic>Arabidopsis,</italic> which could be used in experimental model systems. The yeast-like fungal species <italic>Protomyces arabidopsidicola</italic> was previously isolated from the phyllosphere of healthy wild-growing <italic>Arabidopsis</italic>, identified, and characterized. Here we explore the interaction of <italic>P. arabidopsidicola</italic> with <italic>Arabidopsis</italic> and found <italic>P. arabidopsidicola</italic> strain C29 was not pathogenic on <italic>Arabidopsis</italic>, but was able to survive in its phyllosphere environment both in controlled environment chambers in the lab and under natural field conditions. Most importantly, <italic>P. arabidopsidicola</italic> exhibited an immune priming effect on <italic>Arabidopsis</italic>, which showed enhanced disease resistance when subsequently infected with the fungal pathogen <italic>Botrytis cinerea</italic>. 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 <italic>Arabidopsis</italic> immune defense priming by the naturally occurring phyllosphere resident yeast species, <italic>P. arabidopsidicola,</italic> and contribute to establishing a new interaction system for probing the genetics of <italic>Arabidopsis</italic> immunity induced by resident yeast-like fungi.</p>