Global analyses of the genes involved in meristems organization and leaf intitiation

All above ground organs of higher plants are ultimately derived from specialized organogenic structures called shoot apical meristems (SAMs). The SAM exhibits distinctive structural organization, marked by tissue zonation and cell layering. The structure of plant SAMs is correlated with their function, such that new leaves are initiated from the peripheral zone of the SAM and the central zone replenishes new meristematic cells that are lost during organogenesis.

Experiments are proposed to identify and analyze genes required for meristem function and early stages of leaf development in maize. Laser dissection microscopy is a powerful technique that permits the isolation of RNA from specific cell types within fixed plant tissues. RNA collected from 1,000-10,000 cells is sufficient for use in microarray analyses of gene expression, which permit the simultaneous examination of expression profiles of 15,000 to 30,000 genes. The relatively large size of the maize vegetative meristem, approximately 250 meristematic cells are recruited into the incipient maize leaf, renders this plant especially tractable for this experimental system.

The laser-capture microdissection/microarray technique will be used to capture cells from specific domains of the maize meristem and newly-formed leaf primordia for use in comparative analyses of global gene expression. The differential expression patterns of candidate genes will be verified by more traditional analyses (RT-PCR, RNA gel blot hybridization and in situ hybridization) of transcript accumulation in maize tissues. These experiments will microdissect gene expression patterns in meristems and leaf primordia, and promise to provide novel insight into mechanisms of plant development.