A Barley ROP GTPase ACTIVATING PROTEIN Associates with Microtubules and Regulates Entry of the Barley Powdery Mildew Fungus into Leaf Epidermal Cells

ABSTRACTPlant immunity is overcome by pathogens by the means of secreted effectors. Host effector targets might be proteins acting in pathogen defense or serve demands of the pathogen. The barley ROP GTPase HvRACB is involved in entry of the powdery mildew fungusBlumeria graminisf.sp.hordei (Bgh)into barley epidermal cells. We found that HvRACB interacts with theROP-interactive peptide 1 (ROPIP1) that is encoded on the active non-long terminal repeat retroelement Eg-R1 ofBgh. Over-expression of ROPIP1 in barley epidermal cells and host-induced post-transcriptional gene silencing (HIGS) ofROPIP1suggested that ROPIP1 is involved in virulence ofBgh. Bimolecular fluorescence complementation and co-localization supported that ROPIP1 can interact with activated HvRACB in planta. We show that ROPIP1 is expressed byBghon barley and translocated into the cytoplasm of infected barley cells. ROPIP1 is recruited to microtubules upon co-expression of MICROTUBULE ASSOCIATED ROP GTPase ACTIVATING PROTEIN (HvMAGAP1) and can destabilize cortical microtubules.BghROPIP might target HvRACB and manipulate host cell microtubule organization for facilitated host cell entry. Data suggest a possible neo-functionalization of retroelement-derived transcripts for the evolution of a pathogen virulence effector.

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ROP INTERACTIVE PARTNER b interacts with RACB and supports fungal penetration into barley epidermal cells

10.1101/750265 ◽

2019 ◽

Cited By ~ 3

Author(s):

Christopher McCollum ◽

Stefan Engelhardt ◽

Lukas Weiss ◽

Ralph Hückelhoven

Keyword(s):

Plasma Membrane ◽

Powdery Mildew ◽

Coiled Coil ◽

Cell Polarization ◽

Epidermal Cells ◽

In Planta ◽

Powdery Mildew Fungus ◽

Susceptibility Factor ◽

Polar Cell ◽

Barley Powdery Mildew

AbstractRHO of Plants (ROP) G-proteins are key components of cell polarization processes in plant development. The barley (Hordeum vulgare) ROP protein RACB, is a susceptibility factor in the interaction of barley with the barley powdery mildew fungus Blumeria graminis f.sp. hordei (Bgh). RACB also drives polar cell development, and this function might be coopted during formation of fungal haustoria in barley epidermal cells. In order to understand RACB signaling during the interaction of barley with Bgh, we searched for potential downstream interactors of RACB. Here, we show that ROP INTERACTIVE PARTNER b (RIPb, synonym: INTERACTOR OF CONSTITUTIVE ACTIVE ROP b; ICRb) directly interacts with RACB in yeast and in planta. Over-expression of RIPb supports susceptibility of barley to Bgh. RIPb further interacts with itself at microtubules. However, the interaction with activated RACB takes place at the plasma membrane. Both, RIPb and RACB are recruited to the site of fungal attack around the neck of developing haustoria suggesting locally enhanced ROP activity. We further assigned different functions to different domains of the RIPb protein. The N-terminal coiled-coil CC1 domain is required for microtubule localization, while the C-terminal coiled-coil CC2 domain is sufficient to interact with RACB and to fulfill a function in susceptibility at the plasma membrane. Hence, RIPb appears to be localized at microtubules and is then recruited by activated RACB for a function at the plasma membrane during formation of the haustorial complex.One Sentence summaryRIPb acts downstream of the powdery mildew susceptibility factor RACB of barley and influences susceptibility

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A Small GTP-Binding Host Protein Is Required for Entry of Powdery Mildew Fungus into Epidermal Cells of Barley

PLANT PHYSIOLOGY ◽

10.1104/pp.010805 ◽

2002 ◽

Vol 128 (4) ◽

pp. 1447-1454 ◽

Cited By ~ 97

Author(s):

Holger Schultheiss ◽

Cornelia Dechert ◽

Karl-Heinz Kogel ◽

Ralph Hückelhoven

Keyword(s):

Powdery Mildew ◽

Epidermal Cells ◽

Host Protein ◽

Powdery Mildew Fungus ◽

Gtp Binding

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Differential Gene Expression in Individual Papilla-Resistant and Powdery Mildew-Infected Barley Epidermal Cells

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2004.17.7.729 ◽

2004 ◽

Vol 17 (7) ◽

pp. 729-738 ◽

Cited By ~ 40

Author(s):

Torben Gjetting ◽

Timothy L. W. Carver ◽

Leif Skøt ◽

Michael F. Lyngkjær

Keyword(s):

Gene Expression ◽

Powdery Mildew ◽

Single Cell ◽

Pcr Amplification ◽

Epidermal Cells ◽

Powdery Mildew Fungus ◽

Pathogenesis Related Protein ◽

Infected Cells ◽

Transcript Profiles ◽

Microarray Expression

Resistance and susceptibility in barley to the powdery mildew fungus (Blumeria graminis f. sp. hordei) is determined at the single-cell level. Even in genetically compatible interactions, attacked plant epidermal cells defend themselves against attempted fungal penetration by localized responses leading to papilla deposition and reinforcement of their cell wall. This conveys a race-nonspecific form of resistance. However, this defense is not complete, and a proportion of penetration attempts succeed in infection. The resultant mixture of infected and uninfected leaf cells makes it impossible to relate powdery mildew-induced gene expression in whole leaves or even dissected epidermal tissues to resistance or susceptibility. A method for generating transcript profiles from individual barley epidermal cells was established and proven useful for analyzing resistant and successfully infected cells separately. Contents of single epidermal cells (resistant, infected, and unattacked controls) were collected, and after cDNA synthesis and PCR amplification, the resulting sample was hybridized to dot-blots spotted with genes, including some previously reported to be induced upon pathogen attack. Transcripts of several genes, (e.g., PR1a, encoding a pathogenesis related protein, and GLP4, encoding a germin-like protein) accumulated specifically in resistant cells, while GRP94, encoding a molecular chaperone, accumulated in infected cells. Thus, the single-cell method allows discrimination of transcript profiles from resistant and infected cells. The method will be useful for microarray expression profiling for simultaneous analysis of many genes.

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Defense reactions of barley cultivars to an inappropriate forma specialis of the powdery mildew fungus of gramineous plants

Canadian Journal of Botany ◽

10.1139/b84-287 ◽

1984 ◽

Vol 62 (10) ◽

pp. 2114-2117 ◽

Cited By ~ 27

Author(s):

Y. Tosa ◽

J. Shishiyama

Keyword(s):

Powdery Mildew ◽

Colony Growth ◽

Epidermal Cells ◽

Colony Development ◽

Powdery Mildew Fungus ◽

Barley Cultivars ◽

Cellular Defense ◽

Defense Reactions ◽

Forma Specialis ◽

Fluorescent Cells

Cellular defense reactions in five barley cultivars against Erysiphe graminis f. sp. tritici were examined in the course of primary and secondary penetrations. In cv. Kairyobozu-mugi, 35% of infection attempts were stopped at fluorescent papillae, and the others (65%) induced fluorescing of epidermal cells, resulting in the failure of the formation of primary haustoria. In the other cultivars ('H.E.S.4', 'Russian No. 12', 'Goseshikoku', and 'Turkey 290') the penetration failures associated with fluorescent papillae reached 50–75%, but the infection attempts that induced the fluorescing of epidermal cells were fewer than 20%. Consequently 10–30% of the germlings that attempted penetration successfully formed normal primary haustoria 48 h after inoculation. In cv. Goseshikoku, cv. Russian No. 12, and cv. H.E.S.4, 50–75% of the epidermal cells that contained the primary haustoria were fluorescent 7 days after inoculation, and colony growth was severely restricted. In cv. Turkey 290 such fluorescent cells scarcely occurred and colonies developed comparatively well. On this cultivar conidia were produced 5–6 days after inoculation, but only in small quantities. This restriction of colony development was mainly attributable to the inhibition of the formation of secondary haustoria by fluorescent papillae. These results indicate that there are differences among barley cultivars in cellular defense reactions against the wheat powdery mildew fungus and suggest that the formation of papillae during the course of primary penetration is not necessarily an essential factor in the resistance of barley to this inappropriate forma specialis.

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