Transglutaminase, an enzyme involved in flower senescence and developmental cell death.

To acquire further knowledge on flower senescence and developmental cell death (DCD), we examined protein-protein and protein-polyamine covalent interactions mediated by transglutaminase (TGase) in the tobacco corolla model. In tobacco, corolla senescence proceeds acropetally and is characterised by the formation of a basal abscission zone (AZ) and by changes in the orientation of corolla teeth. TGase, present in various cell compartments, was analysed by using the Arabidopsis thaliana TGase antibody. A 58-kDa form was immunorecognised in microsomal, plastidial (together with a 38-kDa band) and cell wall fraction; a 52-kDa protein was found only in the soluble fraction. The activity reached the maximum at the "no-return point" of senescence corresponding to AZ formation. TGase enzyme activity was also detected in microsome, soluble, plastid, and cell wall fractions. Our results suggest that TGase may be released in the cell wall through the Golgi vesicles. In particular, the cell wall TGase activity could be involved in cell wall strengthening, being especially active where the corolla teeth curl, and during the formation of the AZ.