Sorting activities in plant cells

Eucaryotic cells (plants, animals, fungi, etc.) are subdivided in membrane-bound compartments (organelles), such as the nucleus, mitochondria, chloroplasts, vacuoles, etc. Most organellar proteins are encoded in the nucleus and synthesized in the cytoplasm. Proper sorting of proteins is required to establish and maintain organellar identity. Molecular machineries at the organelle surfaces specifically recognize targeting sequences of their cognate proteins and mediate their translocation across membranes. Proteins destined for the vacuoles are first translocated across the endoplasmic reticulum membrane, packaged into vesicles, transported to the Golgi, where they are sorted into specific vesicles and subsequently carried to the different types of vacuoles. Though plant cells share many features with animal and yeast cells, chloroplasts and distinct lytic and storage vacuoles are unique to plants. Here, we discuss import of proteins into the chloroplast as well as selective sorting of proteins to either the lytic or the storage vacuole.