In the petals of carnation flowers, the phytohormone ethylene is involved in the initiation and regulation of petal senescence. Here Dr. Woodson aims to investigate the molecular mechanisms involved in petal senescence, and determine how ethylene acts to initiate this developmental program. His approach to the problem is to clone genes that are expressed during carnation petal senescence and study how the expression of these genes is regulated both during the temporal development of senescence and by ethylene. He will use these cloned cDNAs as hybridization probes to determine the relative abundance of the mRNAs they represent during the senescence of petals and in response to ethylene treatment. He will determine the spatial distribution of these senescence specific mRNAs by in situ hybridization. Transcriptional regulation of senescence specific genes will be assessed by nuclear run off experiments. He will correlate senescence specific genes to gene products by in vitro translation of hybrid selected mRNAs. Expression of antisense RNA will be used to determine if these genes are essential for senescence. Selected cDNAs will be used to isolate genomic cones for analysis of the cis elements which determine the expression of these genes. Gene chimeras will be constructed that contain the 5' flanking sequences of these genes and the coding sequence for the reporter gene beta-glucuronidase (GUS). Following transformation of carnations and petunias, the capacity for the promoters from senescence specific genes to direct the developmental and/or hormonal regulation of gene expression will be assessed by assaying for GUS activity. %%% Senescence represents the final stage in the development of a whole plant, organ tissue or cell. The flower is often the organ with the shortest life span, and as such provides a useful tissue for studying the mechanisms underlying control of senescence.
