Science http://doi.org/bvr6 (2016)
Since the discovery of systemin in 1991, the number of reported pathways involving hormone-like small peptides has exploded. This type of signalling is now emerging as crucial in many aspects of development, and the Arabidopsis genome encodes more than 1,000 peptides. Before being sensed by their cognate membrane receptors, peptides must undergo post-translational processing to become biologically active.
Katharina Schardon and colleagues, from the University of Hohenheim, Stuttgart, have focused on the abscission peptide INFLORESCENCE DEFICIENT IN ABSCISSION (IDA), which is necessary for shedding floral organs, such as petals, that have no function after pollination. To identify which of the many proteases are involved in the maturation of IDA, they expressed, at the site of abscission, modified subtilase inhibitors isolated from a pathogenic oomycete. This neat biochemical trick phenocopied the ida mutant, bypassing functional redundancy as there were more than 50 candidates. Individual assays later identified the three subtilases that cleave the IDA pro-peptide to produce an active 14-amino-acid-long active peptide.
The functional redundancy of many plant genes makes traditional forward genetics increasingly difficult. This study presents an innovative technique, taking advantage of a biological weapon from a plant pest, to biochemically disrupt a developmental pathway in a model species and solve a biological question.