Metabolic aspects of organogenesis in the shoot apical meristem.

Research over the last decade has led to tremendous advances in the characterization of the transcriptional networks involved in the initiation and maintenance of the shoot apical meristem (SAM), as well as the factors involved in the formation and development of leaves by this organ. However, one aspect of the SAM that has received rather limited attention is the fact that it is characterized by being heterotrophic, in contrast to the majority of cells and tissues immediately derived from it which rapidly undergo differentiation to form photosythetically active, autotrophic organs. This clear physiological and biochemical distinction of the SAM from the surrounding tissue raises interesting questions as to what controls the transition from heterotrophic to autotrophic growth, the nature and sequence of the metabolic events that must occur on this transition, as well as basic questions as to the potential interaction of development and metabolism in this small but essential organ of the plant. In this review, an overview is provided of present knowledge in this area, as well as some recent data that provide an insight into the potential intertwining of metabolic and developmental mechanisms during leaf initiation.