Formation, maintenance and function of the shoot apical meristem in rice

In higher plants, the process of embryogenesis establishes the plant body plan (body axes). On the basis of positional information specified by the body axes, the shoot apical meristem (SAM) and root apical meristem (RAM) differentiate at fixed positions early in embryogenesis. After germination, SAM and RAM are responsible for the development of the above-ground and below-ground parts, respectively, of the plant. Because of the importance of SAM function in plant development, the mechanisms of SAM formation during embryogenesis and of SAM maintenance and function in post-embryonic development are priority questions in plant developmental biology. Recent advances in molecular and genetic analysis of morphogenetic mutations in Arabidopsis have revealed several components required for SAM formation, maintenance and function. Although these processes are fundamental to the life cycle of every plant, conservation of the components does not explain the diversity of plant morphologies. Rice is used as a model plant of the grass family and of monocots because of the progress in research infrastructure, especially the collection of unique mutations and genome information. In comparison with the dicot Arabidopsis, rice has many unique organs or processes of development. This review summarizes what is known of the processes of SAM formation, maintenance and function in rice.