Clp1

Crosstalk between the UPR and pathways controlling pathogenic development is mediated by protein-protein interactions between the UPR regulator Cib1 and the developmental regulator Clp1.

We show that increased ER stress resistance is connected to Clp1-dependent alterations of Cib1 phosphorylation, protein stability and UPR gene expression.

Cib1/Clp1 complex formation results in mutual modification of the connected regulatory networks thereby aligning fungal proliferation in planta, efficient effector secretion with increased ER stress tolerance and long-term UPR activation in planta.

Thus, the interaction between Cib1 and Clp1 constitutes a checkpoint to time developmental progression and increased secretion of effector proteins at the onset of biotrophic development.

we characterize the homologs of the central UPR regulatory proteins Hac1 ... and Inositol Requiring Enzyme1 in the plant pathogenic fungus Ustilago maydis and demonstrate that the UPR is tightly interlinked with the b mating-type-dependent signaling pathway that regulates pathogenic development.

The unusual C-terminal extension of the U. maydis Hac1 homolog, Cib1 (for Clp1 interacting bZIP1), mediates direct interaction with Clp1.

The interaction between Clp1 and Cib1 promotes stabilization of Clp1, resulting in enhanced ER stress tolerance that prevents deleterious UPR hyperactivation.

Exact timing of UPR is required for virulence, since premature activation interferes with the b-dependent switch from budding to filamentous growth.

The concerted interaction of Clp1 with Rbf1 and bW coordinates a- and b-dependent cell cycle control and ensures cell cycle release and progression at the onset of biotrophic development.

Clp1 interaction with bW blocks b-dependent functions, such as the b-dependent G2 cell cycle arrest and dimorphic switching.

The interaction of Clp1 with Rbf1 results in the repression of the a-dependent pheromone pathway, conjugation tube formation, and the a-induced G2 cell cycle arrest.

Here, we show that bW, one of the two homeodomain transcription factors encoded by the b mating-type locus, and the zinc-finger transcription factor Rbf1, a master regulator for pathogenic development, interact with Clp1

we identify Cib1, a previously undiscovered bZIP transcription factor required for pathogenic development, as a Clp1-interacting protein

Here, we show that bW, one of the two homeodomain transcription factors encoded by the b mating-type locus, and the zinc-finger transcription factor Rbf1, a master regulator for pathogenic development, interact with Clp1