A novel function for XXXX CYCLASE1 in programmed cell death revealed by iTRAQ analysis of extracellular matrix proteins.

@entity3785 @entity66 @entity24194 @entity18639 @entity958 @entity855
UNASSIGNED: Programmed cell death is essential for plant development and stress adaptation. A detailed understanding of the signal transduction pathways that regulate plant programmed cell death requires identification of the underpinning protein networks. Here, we have used a protagonist and antagonist of programmed cell death triggered by @entity18639 as probes to identify key cell death regulatory proteins in @entity958 . Our hypothesis was that changes in the abundance of cell death-regulatory proteins induced by the protagonist should be blocked or attenuated by concurrent treatment with the antagonist. We focused on proteins present in the mobile phase of the extracellular matrix on the basis that they are important for cell-cell communications during growth and stress-adaptive responses. @entity3785 , a plant hormone that promotes programmed cell death, and exogenous @entity855 , which can block @entity18639 -induced cell death, were used to treat @entity958 cell suspension cultures prior to isobaric-tagged relative and absolute quantitation analysis of secreted proteins. A total of 33 proteins, whose response to @entity3785 was suppressed by @entity855 , were identified as putative cell death-regulatory proteins. Among these was CYCLASE1, which was selected for further analysis using reverse genetics. Plants in which CYCLASE1 gene expression was knocked out by insertion of a transfer-DNA sequence manifested dramatically increased cell death when exposed to @entity18639 or a bacterial pathogen that triggers the @entity66 . Although pathogen inoculation altered CYCLASE1 gene expression, multiplication of bacterial pathogens was indistinguishable between wildtype and CYCLASE1 knockout plants. However, remarkably severe @entity24194 symptoms developed on gene knockout plants in response to inoculation with either a virulent bacterial pathogen or a disabled mutant that is incapable of causing disease in wildtype plants. These results show that CYCLASE1, which had no known function hitherto, is a negative regulator of cell death and regulates pathogen-induced symptom development in @entity958 .
