ARS | Publication request: MOLECULAR ANALYSIS OF THE INTERACTION OF ETHYLENE AND AUXIN DURING FLOWER ABSCISSION

Submitted to: Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: April 28, 2009
Publication Date: N/A

Technical Abstract: Abscission, the separation of organs from the parent plant, results in postharvest quality loss in many ornamentals and other fresh produce. The process is initiated by changes in the auxin gradient across the abscission zone (AZ), is triggered by ethylene, and may be accelerated by postharvest stress. Although changes in gene expression have been correlated with the ethylene-mediated execution of abscission, there is almost no information on the molecular and biochemical basis of the increase in sensitivity of the AZ to ethylene. We examined transcriptome changes in the tomato (Solanum lycopersicum Mill.) flower AZ during the rapid acquisition of ethylene sensitivity following flower removal, which depletes the AZ from auxin. Microarray analysis using Affymetrix Tomato GeneChip revealed changes in expression, occurring prior to and during pedicel abscission, of many genes with possible regulatory functions. They included a range of auxin- and ethylene-related transcription factors (TFs), other TFs that are transiently induced just after flower removal, and a set of novel AZ-specific genes. To facilitate functional studies we implemented and efficient Virus-Induced Gene Silencing (VIGS) system in tomato using tobacco rattle virus (TRV) and an anthocyanin regulatory gene (Lc) as a silencing reporter. A phenotype showing a significant delay in pedicel abscission in response to auxin depletion (obtained by flower removal) was observed when we silenced several novel AZ-specific genes. These results shed light on the mechanism of increased sensitivity of the AZ to ethylene, and further expand our knowledge of auxin-ethylene cross talk during the abscission process.