Figure 9.

Tentative Model of the Role of the See1-SGT1 Interaction during U. maydis Tumor Formation.

The SGT1 protein is known to occur in the cytoplasmic and nuclear pools (Hoser et al., 2013). In U. maydis wild-type infections, activated unidentified maize kinase (UMK) triggers the phosphorylation of SGT1 at a monocot-specific target site. The See1 effector binds to SGT1, interferes with its phosphorylation status, and thereby disturbs the subcellular distribution (i.e., transport into the nucleus). This misbalancing of SGT1 phosphorylation and distribution contributes to the induction of cell cycle genes, leading to the induction of tumorous division.