Heterotrimeric G Protein Signaling in Filamentous Fungi *

Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521, USA.
Annual Review of Microbiology (Impact Factor: 12.18). 02/2007; 61(1):423-52. DOI: 10.1146/annurev.micro.61.080706.093432
Source: PubMed


Filamentous fungi are multicellular eukaryotic organisms known for nutrient recycling as well as for antibiotic and food production. This group of organisms also contains the most devastating plant pathogens and several important human pathogens. Since the first report of heterotrimeric G proteins in filamentous fungi in 1993, it has been demonstrated that G proteins are essential for growth, asexual and sexual development, and virulence in both animal and plant pathogenic filamentous species. Numerous G protein subunit and G protein-coupled receptor genes have been identified, many from whole-genome sequences. Several regulatory pathways have now been delineated, including those for nutrient sensing, pheromone response and mating, and pathogenesis. This review provides a comparative analysis of G protein pathways in several filamentous species, with discussion of both unifying themes and important unique signaling paradigms.

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    • "Heterotrimeric GTP-binding proteins (G proteins), classically consisting of Ga, Gb, and Gg subunits, are essential signal transduction elements in most eukaryotes . In animals and fungi, ligand perception by G protein-coupled receptors leads to replacement of GDP with GTP in Ga, triggering activation of the heterotrimer (Li et al., 2007; Oldham and Hamm, 2008). Upon activation, GTP-bound Ga and Gbg are released and interact with downstream effectors, thereby transmitting signals to multiple intracellular signaling cascades. "
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    ABSTRACT: In animals, heterotrimeric G proteins, comprising Gα, Gβ and Gγ subunits, are molecular switches whose function tightly depends on Gα and Gβγ interaction. Intriguingly, in Arabidopsis thaliana, multiple defense responses involve Gβγ, but not Gα. We report here that the Gβγ dimer directly partners with extra-large G-proteins (XLGs) to mediate plant immunity. Arabidopsis mutants deficient in XLGs, Gβ and Gγ are similarly compromised in several pathogen defense responses, including disease development and production of reactive oxygen species. Genetic analysis of double, triple and quadruple mutants confirmed that XLGs and Gβγ functionally interact in the same defense signaling pathways. In addition, mutations in XLG2 suppressed the seedling lethal and cell death phenotypes of bir1 mutants in an identical way as reported for agb1 mutants. Yeast-three-hybrid and bimolecular fluorescent complementation assays revealed that XLG2 physically interacts with all three possible Gβγ dimers at the plasma membrane. Phylogenetic analysis indicated a close relationship between XLGs and plant Gα subunits, placing the divergence point at the dawn of land plant evolution. Based on these findings we conclude that XLGs form functional complexes with Gβγ dimers, although the mechanism of action of these complexes, including activation/deactivation, must be radically different form the one used by the canonical Gα subunit and are not likely to share the same receptors. Accordingly, XLGs expand the repertoire of heterotrimeric G proteins in plants, and reveal a higher level of diversity in heterotrimeric G protein signaling. Copyright © 2015, American Society of Plant Biologists.
    Plant physiology 01/2015; 167(3). DOI:10.1104/pp.114.255703 · 6.84 Impact Factor
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    • "Latent infection caused by this pathogen has often been noted in flowers and developing fruit and there is strong evidence that susceptibility to grey mould increases as fruit ripens (Williamson et al., 2007). The progression of the infection from latent stage in unripe fruit to symptomatic disease in ripe fruit is not fully understood, but it is thought to be influenced by host factors. "
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    ABSTRACT: Botrytis cinerea, the main pathogen of strawberry, has the ability to remain quiescent in unripe tissue and develop disease symptoms in ripe fruit. As strawberry ripening is characterized by an increase of aroma compounds, the role of volatile emission in the development of infection was investigated. Thirty-five strawberry volatile organic compounds (VOCs) were tested on B. cinerea in vitro and volatile emission was analysed in strawberry harvested at four ripening stages by headspace solid-phase microextraction/gas chromatography-mass spectrometry and proton transfer reaction- time of flight-mass spectrometry. The coupling of such datasets made it possible to conclude that key strawberry aroma compounds stimulate B. cinerea conidial germination and some typical wound-volatiles stimulate pathogen’ conidial germination or mycelial growth. This study is the first report of fungal stimulation by some VOCs naturally occurring in strawberry: the esters ethyl butanoate, cis-3-hexenyl acetate, trans-2-hexenyl acetate, methyl butanoate and hexyl butanoate, the furanones furaneol and mesifurane, and the alcohol trans-2-hexenol. The results of our work provide advances in understanding the functional role of fruit VOCs and suggest for the first time that fruit VOCs may influence the resuming of B. cinerea from the latent phase and that they could favour the invasive growth of B. cinerea after wounding. In particular, ethyl butanoate and furaneol could signal strawberry ripening, and the green leaf volatiles trans-2-hexenol, trans 2-hexenyl acetate and cis-3-hexenyl acetate could signal the presence of damaged tissues, that are easier sites for penetration by B. cinerea.This article is protected by copyright. All rights reserved.
    Plant Pathology 08/2014; 64(3). DOI:10.1111/ppa.12287 · 2.12 Impact Factor
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    • "In case of activation of the GPCR, a conformational change of the receptor results in an exchange of GDP for GTP at the G alpha subunit. The active G alpha subunit dissociates from the tightly bound G beta gamma dimer and both are impacting their effectors to affect regulatory pathways of secondary messengers [16, 17]. "
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    ABSTRACT: Background Crosstalk between the signalling pathways responding to light–dark cycles and those triggering the adaptation of metabolism to the environment is known to occur in various organisms. This interrelationship of light response and nutrient sigalling is crucial for health and fitness. The tropical ascomycete Trichoderma reesei (syn. Hypocrea jecorina) represents one of the most efficient plant cell wall degraders. Regulation of the enzymes required for this process is affected by nutritional signals as well as other environmental signals including light. Therefore we aimed to elucidate the interrelationship between nutrient and light signaling and how the light signal is transmitted to downstream pathways. Results We found that the targets of the light regulatory protein ENV1 in light show considerable overlap with those of the heterotrimeric G-protein components PhLP1, GNB1 and GNG1. Detailed investigation of a regulatory interrelationship of these components with ENV1 under conditions of early and late light response indicated a transcriptional mutual regulation between PhLP1 and ENV1, which appears to dampen nutrient signalling during early light response, presumably to free resources for protective measures prior to adaptation of metabolism to light. Investigating the downstream part of the cascade we found support for the hypothesis that ENV1 is necessary for cAMP mediated regulation of a considerable part of the core functions of the output pathway of this cascade, including regulation of glycoside hydrolase genes and those involved in nitrogen, sulphur and amino acid metabolism. Conclusions ENV1 and PhLP1 are mutual regulators connecting light signaling with nutrient signaling, with ENV1 triggering the output pathway by influencing cAMP levels. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-425) contains supplementary material, which is available to authorized users.
    BMC Genomics 06/2014; 15(1):425. DOI:10.1186/1471-2164-15-425 · 3.99 Impact Factor
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