Control of Arabidopsis immune and developmental gene expression through phosphorylation of VQ-motif containing transcriptional co-regulators.

Mitogen-activated protein kinases (MAPKs) are highly conserved in all eukaryotes and control cellular responses through phosphorylation of target proteins, which are often transcriptional regulators.Our interest in MAPKs relevant for plant immunity led us to analyse a subclass of VQ-motif containing proteins (VQPs) that we termed MVQs (for MAPK-targeted VQPs).MVQs bind specific WRKY transcription factors to modulate their functions.Here, we present work on MVQ9 (also known as IKU1) that acts in the HAIKU pathway for seed size control in Arabidopsis thaliana.Unlike its interactor (WRKY10), MVQ9 is predicted as an unstructured intrinsically disordered protein and can undergo liquid-liquid phase separation into condensates.We aim to understand how condensate dynamics regulated by MAPK signaling control MVQ9 functions in endosperm development but also impinge on plant immunity.