MPK4 interacting proteins in guard cells through AP-MS

Plants are often challenged by numerous biotic and abiotic environmental stresses. They have evolved efficient signaling networks in response to the environmental challenges, such as pathogen invasion, drought, CO2 changes. Guard cells are specialized epidermal cells enclosing pores on leaf surface, aka, stomata. Stomatal guard cells are at the frontline of biotic and abiotic stress responses. The opening and closing of stomata are regulated by a sophisticated intracellular signaling networks. Mitogen-activated protein kinase 4 (MPK4) was first identified as negative regulator in systemic acquired resistance (SAR). It was also play important roles in cytokinesis, reproduction, and photosynthesis. MPK4 has higher expression levels in plant guard cells than in mesophyll cells. Arabidopsis mpk4 mutant has higher levels of salicylic acid (SA) and reactive oxygen species (ROS), which are related with stomatal movement. The specific function of MPK4 in guard cells is unknown. In order to understand MPK4 functions in guard cells, it is essential to investigate MPK4-associated protein complex. Here we focus on identification of guard cell specific MPK4 complex using affinity purification following by mass spectrometry (AP-MS). Potential substrates were selected and validated with yeast two hybrid (Y2H).