Cell type-dependent localization of MLO proteins.

Mildew resistance locus O (MLO) proteins are transmembrane proteins that mediate cell-cell communication in plants. We recently demonstrated the importance of subcellular localization to MLO function during pollen tube reception. NORTIA (NTA), the MLO protein involved in this process, localizes to the Golgi of the synergid cell before interaction with the pollen tube. MLO proteins that can substitute for NTA's function in this pathway all partially localize with the same Golgi marker in the synergid cell. In this study, we report that MLO subcellular localization is cell type-dependent, with different distributions of some MLOs observed when ectopically expressed in the epidermal cells of tobacco and Arabidopsis compared to synergids. This dependency may be due to co-factors that influence MLO function within a given cell type, providing an intriguing new target for understanding MLO distribution and subsequent function in their respective processes.