Shoot apical meristem ontogenesis in vivo and in vitro

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As the Late Professor Ian Sussex stated in his review (Cell 56: 225, 1989), “The meristems make the plant”. Apical meristems (AMs) are the mother of all cells in plants. They are responsible for the formation of tissues and organs of the primary plant body. Without properly functioning AMs, land plants will not exist. Although recent advances have been made in our understanding of the formation, maintenance, and function of AMs during normal plant development, we still do not fully understand how they are initiated during embryogenesis. Tissue culture and micropropagation of plants are important approaches in commercial plant production. To be successful, AM formation is a must in the newly regenerated plants. Moreover, our understanding of AM initiation from in vitro micropropagated plants is even more limited than in vivo studies. One particularly commercially important plant is the orchid. Unlike other flowering plants, orchid AMs are absent during embryo development; instead, they are initiated after seed germination. This begs the questions as to why orchids choose this strategy in meristem initiation and what is the mechanism(s) of meristem gene regulation leading to the delay in meristem formation. Since this research program focuses on a central structure which is key to plant development, this research is important to all biologists interested in plant growth and development. The overall goal of this research program is to provide a mechanistic understanding of shoot apical meristem ontogeny in vitro using Arabidopsis embryos as explants and in vivo using the moth orchid, Phalaenopsis, developing embryos and protocorms as our experimental systems. We anticipate that we can unravel key events in meristem initiation and the associated regulatory mechanism(s) using these experimental systems. Besides theoretical contributions, we will be able to devise and/or recommend new protocols for plant micropropagation. The knowledge concerning meristem formation in vivo and in vitro is the foundation for plant biotechnology applications. The information will benefit both layman and scientists interested in plant growth and development and also to commercial growers nationally and internationally, interested in plant production. If shoot regeneration is guaranteed, this will lead to more successes in transformation studies and the generation of genetically modified plants. Climate change in recent years has brought uncertainty in crop production and yield. Our ability to guarantee shoot production in micropropagated plants will ensure plant production and improve yield. A better understanding of meristem formation in orchids will help in the conservation of species from natural habitat erosion, as apical meristem formation is a prerequisite for further growth and development. This positive outcome will also assist in the commercialization of this unique group of flowering plants.