MgHog1 Regulates Dimorphism and Pathogenicity in the Fungal Wheat Pathogen Mycosphaerella graminicola

Abstract

The dimorphic ascomycete pathogen Mycosphaerella graminicola switches from a yeastlike form to an infectious filamentous form that penetrates the host foliage through stomata. We examined the biological function of the mitogen-activated protein kinase-encoding gene MgHog1 in M. graminicola. Interestingly, MgHog1 mutants were unable to switch to filamentous growth on water agar that mimics the nutritionally poor conditions on the foliar surface and, hence, exclusively developed by a yeastlike budding process. Consequently, due to impaired initiation of infectious germ tubes, as revealed by detailed in planta cytological analyses, the MgHog1 mutants failed to infect wheat leaves. We, therefore, conclude that MgHog1 is a new pathogenicity factor involved in the regulation of dimorphism in M. graminicola. Furthermore, MgHog1 mutants are osmosensitive, resistant to phenylpyrrole and dicarboximide fungicides, and do not melanize.

QTL mapping of temperature sensitivity reveals candidate genes for thermal adaptation and growth morphology in the plant pathogenic fungus Zymoseptoria tritici

“…Our results also indicate that growth rate is not determined solely by the colony morphology, as we found three growth QTLs that were not associated with the dimorphism phenotype. In Z. tritici the switch between morphologies can be induced in vitro by changing from a nutrient-rich medium, which favors yeast-like growth, to a poor medium that favors hyphal growth (Mehrabi and Kema, 2006;Mehrabi et al, 2006b). We found that temperature significantly affected dimorphism in our mapping populations, with more progeny exhibiting hyphal growth at 22°C compared with 15°C.…”

“…Changes in cell membrane fluidity are thought to be a common mechanism for microorganisms to adapt to changing temperatures (Leach and Cowen, 2014). A mutant study (Mehrabi et al, 2006b) of the Z. tritici ortholog HOG1, MgHog1 (JGI ID: 76502), found higher melanization associated with greater hyphal growth as well as larger colony sizes, the same pattern of phenotypes exhibited by the chromosome 10 TS QTL. Many of the chromosome 10 QTL pleiotropic effects observed in this study were found at 15°C but not at 22°C.…”

“…Although Z. tritici is considered a filamentous fungus that grows mainly as hyphae, a yeast-like morphology is often observed in culture on rich media, suggesting that Z. tritici is dimorphic (Mehrabi and Kema, 2006;Mehrabi et al, 2006b;Nadal et al, 2008). To determine if the yeast/hyphae dimorphism can be mapped, we conducted a visual inspection of the digital images to classify the colonies of each isolate as either hyphal-or yeast-like.…”

Mitogen-activated protein kinase signaling pathways of the tangerine pathotype of Alternaria alternata

“…Graminicola, C. heterostrophus and F. graminearum. [76][77][78][79][80][81][82][83][84][85][86][87][88][89] The A. alternata Hog1 (AaHog1), analogous to the yeast Hog1, has a distinct phosphorylation motif (TGY) required for the hyperosmolarity response. 5 AaHog1 also has a protein kinase ATP-binding region, a MAP kinase and a serine/threonine protein kinase active site.…”

The Mitogen-Activated Protein Kinase Signal Transduction Pathways in Alternaria Species

“…The Hog1-type mutants of M. grisea (Dixon et al, 1999), C. lagenarium (Kojima et al, 2004) and B. oryzae (Moriwaki et al, 2006) remained fully pathogenic on their own hosts. However, MgHog1 disruption mutants of M. graminicola could not infect wheat leaves (Mehrabi et al, 2006b). In C. parasitica, knockout of the Hog1 homolog cpmk1 induced some hypovirulence-associated symptoms including reduction in pigmentation, conidiation, laccase production, and virulence on chestnut tree (Park et al, 2004).…”