Mechanisms of organelle inheritance in dividing plant cells

Membrane-bound organelles are a characteristic feature of eukaryotic cells, providing intracellular compartments that concentrate enzymes, separate distinct biochemical pathways and generate chemical and electrical gradients - crucial to the production of energy and cell signaling processes (Cavalier-Smith 2002). Organelles, in particular plastids, mitochondria, peroxisomes, Golgi and the endoplasmic reticulum (ER), must be present throughout the cell cycle to ensure a continuity of organelles and organelle-derived functions for future generations. During the cell cycle each organelle (or the organelle population) must double in size, divide, and be delivered to its proper location in the daughter cells (Warren and Wickner 1996). For the nucleus, highly organized and elaborate inheritance processes exist, ensuring stringently accurate partitioning of the nuclear genome to each daughter cell. It had been common belief that organelle inheritance was merely the result of stochastic dispersion processes (Huh and Paulsson 2011), and consequently little investigation was conducted into the cellular and molecular mechanisms that may be acting to ensure the continuity of organellar information systems. Evidence from a number of experimental organisms including yeast (Fagarasanu et al. 2010) and plants (Sheahan et.al. 2007), however, indicate that ordered mechanisms exist to ensure organelle continuity during cell division. A growing recognition of organelle association with the cytoskeleton and coordinated movements of organelles during cell division implicates cellular machinery in the mediation ofunbiased organelle inheritance (Sheahan et al. 2004). In this Chapter, we examine current understanding of organelle partitioning to maintain organelle continuity to ensure cellular function in future generations. After a brief introduction to organelle evolution, we focus our discussion on inheritance mechanisms of plastids, mitochondria, peroxisomes, the Golgi and ER. Investigations on the developing and reproducing flowering plant as well as on cell suspension cultures and regenerating protoplasts are considered