Poster: Hormones

Abs # 610: Regulation of Floral Volatile Synthesis in Petunia hybrida during Ethylene-Induced Senescence

Presenter:	Underwood, Beverly A, bev114@ufl.edu
Authors	Underwood, Beverly A (A)   Shibuya, Kenichi  (A)   Loucas, Holly M (A)   Tieman, Denise M (B)   Klee, Harry J (B)   Clark, David G (A)
Affiliations:	(A): Department of Environmental Horticulture, University of Florida (B): Department of Horticulture, University of Florida

In order to study the role of ethylene in floral senescence, we conducted microarray experiments to isolate ethylene-related genes from Petunia hybrida 'Mitchell Diploid' flowers. Three cDNA libraries were made from Petunia flowers from which approximately 7500 clones were sequenced and subjected to bioinformatic analysis to construct a non-redundant set. This unique set of approximately 3500 cDNAs was then spotted onto glass microarrays, and probed with differential populations of cDNAs produced from mRNAs isolated from flowers at various stages of ethylene-induced senescence. Among the genes shown to be ethylene-downregulated were two cDNAs homologous to S-adenosylmethionine carboxyl methyltransferase (SAMT) genes isolated from Clarkia breweri (Ross et al., 1999) and Antirrinhum majus (Negre et al., 2002). SAMTs have been characterized in vitro to catalyze the formation of volatile methyl esters, important components of floral scent in many plant species. Two full length cDNAs were identified from the Petunia EST collection which share 97% nucleotide identity to each other (PhBSMT1 and PhBSMT2). Expression of the genes was found to be tissue specific, with highest expression in petals. Together with analysis of transgenic PhBSMT RNAi plants our results indicate that these genes are responsible for synthesis of methyl benzoate in Petunia petals. The regulation of PhBSMT mRNA levels by ethylene suggest a new role for ethylene in regulating floral scent in Petunia during senescence.