Distinct and Combined Roles of the MAP Kinases of Cochliobolus heterostrophus in Virulence and Stress Responses

Abstract

Pathogenicity mitogen-activated protein kinases (MAPKs), related to yeast FUS3/KSS1, are essential for virulence in fungi, including Cochliobolus heterostrophus, a necrotrophic pathogen causing Southern corn leaf blight. We compared the phenotypes of mutants in three MAPK genes: HOG1, MPS1, and CHK1. The chk1 and mps1 mutants show autolytic appearance, light pigmentation, and dramatic reduction in virulence and conidiation. Similarity of mps1 and chk1 mutants is reflected by coregulation by these two MAPKs of several genes. Unlike chk1, mps1 mutants are female-fertile and form normal-looking appressoria. HOG1 mediates resistance to hyperosmotic and, to a lesser extent, oxidative stress, and is required for stress upregulation of glycerol-3-phosphate phosphatase, transaldolase, and a monosaccharide transporter. Hog1, but not Mps1 or Chk1, was rapidly phosphorylated in response to increased osmolarity. The hog1 mutants have smaller appressoria and cause decreased disease symptoms on maize leaves. Surprisingly, loss of MPS1 in a wild-type or hog1 background improved resistance to some stresses. All three MAPKs contribute to the regulation of central developmental functions under normal and stress conditions, and full virulence cannot be achieved without appropriate input from all three pathways.

A Non-Mendelian MAPK-Generated Hereditary Unit Controlled by a Second MAPK Pathway inPodospora anserina

“…Unlike yeasts, in which many connections between the MAPK pathways have been described, little is known about the entire MAPK network and potential cross-talks in filamentous fungi. Indeed, comparative analyses of the MAPK pathways have been carried out only in Cochliobolus heterostrophus (Igbaria et al 2008) and N. crassa (Maerz et al 2008), although inactivation of the three pathways has been performed in more fungi. Only in N. crassa was the complete inactivation set for the nine kinase genes reported; as in C. heterostrophus, only inactivation of the MAPK gene was achieved (Igbaria et al 2008).…”

“…Indeed, comparative analyses of the MAPK pathways have been carried out only in Cochliobolus heterostrophus (Igbaria et al 2008) and N. crassa (Maerz et al 2008), although inactivation of the three pathways has been performed in more fungi. Only in N. crassa was the complete inactivation set for the nine kinase genes reported; as in C. heterostrophus, only inactivation of the MAPK gene was achieved (Igbaria et al 2008). Moreover, a double mutant inactivated for two MAPKs, the MPK1-like and HOG1-like MAPK of C. heterostrophus, has been described (Igbaria et al 2008).…”

Simple Genetic Tools to Study Fruiting Body Development in Fungi

“…However, true mosaic analysis was carried out for the rcoA mutant of Aspergillus nidulans with blA1 [24] to show that the rcoA gene is required in the cleistothecial wall. True mosaic analysis has also been used in Cochliobolus heterotrophus using the albino mutant [25] to study the role of the Mps1 MAP Kinase, which is the orthologue of PaMpk1 in this species. While Mps1 x Mps1 crosses are sterile, Mps1 x albino ones produce both dark and light pseudothecia.…”

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

“…22 The Fus3 homolog also plays a critical role in virulence of other phytopathogenic fungi, including A. brassicicola, Bipolaris oryzae, Botrytis cinerea, Claviceps purpurea, C. heterostrophus, Colletotrichum lagenarium, Cryphonectria parasitica, Fusarium spp., Mycosphaerella graminicola, Pyrenophora teres, Stagonospora nodorum and Verticillium dahliae. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] The Fus3 homolog (Cek1) is also an important virulence determinant in the opportunistic human pathogen Candida albicans. 38 The AaFus3 gene encoding a homolog of the yeast Fus3-like MAP kinase was cloned and 39 In addition, the Fus3 MAPK-mediated signaling pathway is involved in conidia formation and maturation in A. alternata, since Dfus3 mutant does not produce any conidia.…”