This proposal is designed to identify, isolate, and characterized genes specifically expressed in floral meristems. The novel tobacco (Nicotiana tabacum) "Thin Cell Layer" (TCL) tissue culture system will be used to produce explants containing floral meristems. TCL explants in floral culture conditions produce up to 15 fully differentiated and functional flowers according to the following scheme. Day 7:active cell division; Day 13: organized meristems formed, Day 20: differentiated organs visable. Differential screening of a cDNA library made from Day 13 floral TCL explants will be used to isolate clones for genes transcriptionally expressed at Day 13, but not a Day 7, of culture. Potential meristematic specific genes isolated by this approach will be characterized using in situ hybridization to identify those expressed in floral meristems. Genes of interest will be subjected to molecular and in vitro mutational analysis, facilitated by stable plant transformation, to determine the mechanisms of gene regulation and function during floral initiation. This work should greatly improve our understanding of gene expression in plant development by providing evidence of the factors which control developmentally regulated gene expression, and giving insight to the types of genes required to change the strategy of plant growth.
