|Meir, Shimon -|
|Philosoph-Hadas, Sonia -|
|Sundaresan, Srivignesh -|
|Selvaraj, Vijay -|
|Burd, Shaul -|
|Ophir, Ron -|
|Kochanek, Bettina -|
|Reid, Michael -|
|Lers, Amnon -|
Submitted to: Plant Signaling and Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 2, 2011
Publication Date: April 1, 2011
Repository URL: http://www.landesbioscience.com/journals/psb/article/15043/
Citation: Meir, S., Philosoph-Hadas, S., Sundaresan, S., Selvaraj, V.K., Burd, S., Ophir, R., Kochanek, B., Reid, M.S., Jiang, C., Lers, A. 2011. Identification of defense-related genes newly-associated with tomato flower abscission. Plant Signaling and Behavior. 6:4, 590-593. Interpretive Summary: Abscission is a highly coordinated developmental process that results in shedding of organs at predetermined sites called abscission zones (AZs). A current accepted model of abscission involves four major steps in the abscission pathway: 1) differentiation of the AZ; 2) development and acquisition of the AZ competence to respond to abscission signals; 3) activation of organ abscission; and 4) post-abscission trans-differentiation of a protective layer as the last step in the pathway. A detailed comparative transcriptional survey between laser-microdissected cells from laminar AZ and adjacent petiolar cortical tissue during ethylene-promoted abscission in citrus leaves showed a preferential expression of stress or defensive-related genes in the remaining petiolar cortical tissue. This suggests that the remaining AZ petiolar cortical tissue is likely to be reprogrammed to be better adopted to cope with pathogen or herbivorous insect attacks, as well as be better protected against general abiotic stresses after organ shedding. Here, we expand the repertoire of genes activated in the AZ, and which are likely to be involved in defense responses. We report for the first time on activation during abscission of four genes known to be involved in defense against pathogen attack, including: Cysteine-type endopeptidase, a-Dioxygenase 1 (a-DOX1), HopW-1-1-Interacting protein2 (WIN2), and Stomatal-derived factor-2 (SDF2). This conclusion is based on the following evidence: (a) The expression of these genes was mainly induced at 8-14 h after flower removal, when pedicel abscission was already in progress; (b) this late expression was AZ-specific; and (c) treatments that prevented pedicel abscission, including 1-methylecyclopropene (1-MCP) pretreatment or IAA application, prevented the increase in expression of these genes. This information supports the activation of different defense responses and strategies at the late abscission stages, which enable efficient protection of the exposed tissue toward different environmental stresses.
Technical Abstract: The current abscission model suggests the formation of a post-abscission trans-differentiation of a protective layer as the last step of the process. The present report expands the repertoire of genes activated in the tomato flower abscission zone (AZ), which are likely to be involved in defense responses. We identified four different defense-related genes, including: Cysteine-type endopeptidase, a-Dioxygenase 1 (a-DOX1), HopW-1-1-Interacting protein2 (WIN2), and Stomatal-derived factor-2 (SDF2), that are newly-associated with the late stage of the abscission process. The late expression of these genes, induced at 8-14 h after flower removal when pedicel abscission was already in progress, was AZ-specific, and was inhibited by treatments that prevented pedicel abscission, including 1-methylcyclopropene pretreatment or IAA application. This information supports the activation of different defense responses and strategies at the late abscission stages, which may enable efficient protection of the exposed tissue toward different environmental stresses.