A Yeast STE11 Homologue CoMEKK1 Is Essential for Pathogenesis-Related Morphogenesis in Colletotrichum orbiculare

Abstract

Several signal transduction pathways, including mitogen-activated protein kinase (MAPK) pathways, are involved in appressorium development in Colletotrichum orbiculare, the causal agent of cucumber anthracnose disease. In this study, CoMEKK1, a yeast MAPK kinases (MAPKK) kinase STE11 homolog, was identified as a disrupted gene in an Agrobacterium tumefaciens-mediated transformation mutant. The phenotype of comekk1 disruptant was similar to that of cmk1, a Saccharomyces cerevisiae Fus3/Kss1 MAPK homolog mutant. Moreover, comekk1 and cmk1 mutants were sensitive to high osmotic and salinity stresses, indicating that Comekk1p/Cmk1p signal transduction is involved in stress tolerance. The transformants of the wild type and the comekk1 mutant expressing a constitutively active form of the CoMEKK1 showed slower hyphal growth and abnormal appressorium formation, whereas those of the cmk1 disruptant did not. A Cmk1p-green fluorescent protein (GFP) intracellular localization experiment indicated that nuclear localization of the Cmk1p-GFP fusion protein induced by salt stress was diminished in comekk1 mutants. These results indicate that Comekk1p functions upstream of Cmk1p.

Mitogen-Activated Protein Kinase Signaling in Plant-Interacting Fungi: Distinct Messages from Conserved Messengers

“…More recently, the MAP3K MEKK1 (Cor-Ste11 according to our proposed nomenclature) was found to act upstream of the MAPK Cmk1 (here renamed Cor-Kss1) in C. orbiculare (Sakaguchi et al, 2010). C. orbiculare strains lacking Ste11 and Kss1 both fail to form an appressorium, while nuclear localization of a Kss1-green fluorescent protein fusion is diminished in the ste11 deletion mutants.…”

MAPKK-encoding gene Ste7 in Bipolaris maydis is required for development and morphogenesis

“…One of the cascades, the Chk1-type MAPK cascade, has been focused on as a master regulator of pathogenesis in plant pathogens (Xu 2000;). In many model species of plant pathogen, the Chk1-type MAPK was well characterized (Xu and Hamer 1996;Mayorga and Gold 1999;Mü ller et al 1999;Takano et al 2000;Zheng et al 2000;Bruno et al 2004), although the upstream two kinases, Ste11-type MAPKKK and Ste7-type MAPKK have only been characterized in a few models (Banuett and Herskowitz 1994;Andrews et al 2000;Kim et al 2000;Zhao et al 2005;Sakaguchi et al 2010;Schamber et al 2010). In this study, we identified and characterized Ste7 MAPKK of B. maydis, in order to elucidate the functional roles of Ste7, using null mutant strains (Dste7).…”

“…cinerea, etc. (Andrews et al 2000;Mü ller et al 2003;Zhao et al 2005;Sakaguchi et al 2010;Schamber et al 2010 (Errede et al 1993;Neiman and Herskowitz 1994;Bardwell et al 1996). In addition, interactions of these proteins with a scaffold protein, which is involved in this signaling cascade, were also elucidated in S. cerevisiae and M. grisea (Choi et al 1994;Park et al 2006).…”

“…Previous studies also noted that the Chk1-type MAPK cascade regulated conidiation in M. grisea (Xu and Hamer 1996;Bruno et al 2004;Zhao et al 2005) and Colletotrichum spp. (Kim et al 2000;Takano et al 2000;Sakaguchi et al 2010) as well as B. maydis. On the other hand, the level of regulation of conidial germination was significantly different among these three species; no conidia germinated in B. maydis, a few conidia germinated in M. grisea (Xu and Hamer 1996;Bruno et al 2004;Zhao et al 2005), and a few conidia germinated in water but most conidia germinated in nutrient-rich condition in Colletotrichum spp.…”

“…cinerea DBmp1 (Zheng et al 2000). As mentioned above, MAPK genes have been characterized to compare their functions among pathogens (Xu 2000;), although the upstream MAPKKK and MAPKK genes remain less well-understood in many pathogens, except the species described above (Banuett and Herskowitz 1994;Andrews et al 2000;Kim et al 2000;Zhao et al 2005;Sakaguchi et al 2010;Schamber et al 2010). However, information about MAPKKK and MAPKK will be necessary in order to understand the complete cascades and crosstalk with other MAPK cascades.…”