AUTHOR=Li Xiao , Liu Yuhan , He Qiguang , Li Sipeng , Liu Wenbo , Lin Chunhua , Miao Weiguo 

TITLE=A Candidate Secreted Effector Protein of Rubber Tree Powdery Mildew Fungus Contributes to Infection by Regulating Plant ABA Biosynthesis

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.591387

DOI=10.3389/fmicb.2020.591387

ISSN=1664-302X

ABSTRACT=<p>Powdery mildew infects a wide range of crops and economic plants, causing substantial losses. Rubber trees (<italic>Hevea brasiliensis</italic>) are the primary source of natural rubber, and powdery mildew infection causes significant losses to natural rubber yields. How the causal agent, <italic>Erysiphe quercicola</italic>, establishes successful infection in rubber trees is largely unknown. Previously, 133 candidate secreted effector proteins (CSEPs) were identified in powdery mildew fungus. In this study, we characterize a CSEP named EqCSEP01276 for its function in suppressing host plant defense responses. We show that EqCSEP01276 is a secreted protein and is able to disturb the localization of 9-<italic>cis</italic>-epoxycarotenoid dioxygenase 5 (HbNCED5), a key enzyme in abscisic acid (ABA) biosynthesis in plant cell chloroplasts of <italic>H</italic>. <italic>brasiliensis</italic>. We also show that this effector inhibits ABA biosynthesis, and that in <italic>H</italic>. <italic>brasiliensis</italic> ABA is a positive regulator of the plant immune response against powdery mildew. Our study reveals a strategy by which powdery mildew fungus manipulates plant ABA-mediated defense for a successful infection.</p>