Post-translational maturation of IDA, a peptide signal controlling floral organ abscission in Arabidopsis

ARTICLE HISTORY Received 14 August 2017 Revised 16 October 2017 Accepted 16 October 2017 ABSTRACT The abscission of sepals, petals and stamens in Arabidopsis flowers is controlled by a peptide signal called IDA (Inflorescence Deficient in Abscission). IDA belongs to the large group of small posttranslationally modified signaling peptides that are synthesized as larger precursors and require proteolytic processing and specific side chain modifications for signal biogenesis. Using tissuespecific expression of proteinase inhibitors as a novel approach for loss-of-function analysis, we recently identified the peptidases responsible for IDA maturation within the large family of subtilisin-like proteinases (subtilases; SBTs). Further biochemical and physiological assays identified three SBTs (AtSBT5.2, AtSBT4.12, AtSBT4.13) that cleave the IDA precursor to generate the Nterminus of the mature peptide. The C-terminal processing enzyme(s) remain(s) to be identified. While proline hydroxylation was suggested as additional post-translational modification required for IDA maturation, hydroxylated and non-hydroxylated IDA peptides were found to be equally active in bioassays for abscission.