Abstract
Powdery mildew is one of the most important fungal pathogen diseases. The genome of barley mildew fungus, Blumeria graminis f. sp. hordei (Bgh), encodes a large number of candidate secreted effector proteins (CSEPs). So far, the function and mechanism of most CSEPs remain largely unknown. Here, we identify a Bgh effector CSEP0027, a member of family 41, triggering cell death in Nicotiana benthamiana. CSEP0027 contains a functional signal peptide (SP), verified by yeast secretion assay. We show that CSEP0027 promotes Bgh virulence in barley infection using transient gene expression and host-induced gene silencing (HIGS). Barley catalase HvCAT1 is identified as a CSEP0027 interactor by yeast two-hybrid (Y2H) screening, and the interaction is verified in yeast, in vitro and in vivo. The coexpression of CSEP0027 and HvCAT1 in barley cells results in altered localization of HvCAT1 from the peroxisome to the nucleus. Barley stripe mosaic virus (BSMV)-silencing and transiently-induced gene silencing (TIGS) assays reveal that HvCAT1 is required for barley immunity against Bgh. We propose that CSEP0027 interacts with barley HvCAT1 to regulate the host immunity and likely reactive oxygen species (ROS) homeostasis to promote fungal virulence during barley infection.
Highlights
Powdery mildews are widespread fungal diseases that affect more than 10,000 plant species, such as important cereal crops, economic, and ornamental plants (Glawe, 2008; Dean et al, 2012; Takamatsu, 2013)
B. graminis fungi encode several hundreds of candidate secreted effector proteins (CSEPs), and it is expected that many of the CSEPs contribute to the obligate biotrophy life style of the B. graminis fungi, for example, co-survival with the host cells or tissues
We identify B. graminis f.sp. hordei (Bgh) CSEP0027 that triggers cell death when heterologously expressed in N. benthamiana
Summary
Powdery mildews are widespread fungal diseases that affect more than 10,000 plant species, such as important cereal crops, economic, and ornamental plants (Glawe, 2008; Dean et al, 2012; Takamatsu, 2013). Several Bgh CSEPs/BECs have been functionally characterized with respect to fungal virulence through transient gene expression and hostinduced gene silencing (HIGS) approaches (Bindschedler et al, 2009; Godfrey et al, 2009; Nowara et al, 2010; Spanu et al, 2010; Pedersen et al, 2012; Pliego et al, 2013; Ahmed et al, 2015, 2016; Menardo et al, 2017; Frantzeskakis et al, 2018; Pennington et al, 2019; Li et al, 2021). The function and mode of action of many CSEPs remain largely unclear
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