Location: Crops Pathology and Genetics Research2013 Annual Report
1a. Objectives (from AD-416):
Utilize Virus-induced gene silencing (VIGS)-based gene functional analysis to characterize the function of identified candidate genes that appear to be involved in regulated leaf and flower abscission.
1b. Approach (from AD-416):
Use shotgun proteomics (LC-MS/MS) to collect data on the entire abscission proteome. Protein quantification will be accomplished using di-methylation and spectral counting. Implement the new knowledge regarding regulation of floral organ abscission in Arabidopsis, in the ethylene-induced abscission of agriculturally important plants, i.e., soybean and tomato. Determine if an IDA signaling path is essential for organ abscission in tomato and soybean and determine its interaction with ethylene and auxin signaling.
3. Progress Report:
This agreement was established in support of parent project objective #3 of the in-house project, which is to determine molecular processes in flower senescence for the purposes of developing 'freshness' indicators for cut flowers and future genetic manipulation of flower senescence. A KNOTTED1-LIKE HOMEOBOX transcription factor is highly expressed in both leaf and flower abscission zones (AZs). Reducing abundance of transcripts of this gene in tomato, using both virus induced gene silencing and stable transformation with a silencing construct driven under an abscission-specific promoter, resulted in a striking retardation of pedicel and petiole abscission. In addition, a semi-dominant mutant with up-regulation of this gene showed earlier pedicel and petiole abscission. cDNA microarray and RT-PCR analysis indicated that regulation of abscission by this transcription regulator was based on the responses of auxin signaling and transport genes. Auxin content and a DR5::GUS auxin reporter assay confirmed that this regulator modulated the auxin level and response in abscission zone. Our data demonstrate that this transcriptional regulator plays its crucial role in abscission through modulating auxin gradient and response. Environmental factors significantly influence abscission process. ARS scientists in Davis, California, found that high temperature stimulated flower abscission in tomato using detached flowers without flower removal. Elucidation of underlying molecular mechanism relating to auxin gradient and response/ethylene sensitivity is underway.