Plant TGases, still unclassified, are widespread in higher and lower plants, in several plant organs and probably different isoforms are differently located in various cell compartments: chloro- plasts, mitochondria, cytoplasm, cell walls. They probably exert a mainly structural or conformational role; however, in chloroplasts and mitochondria their roles might be related to the organelles’ specific metabolisms. Transglutaminases appear related to growth (cell cycle, apical growth, seedling growth), differentiation, programmed cell death and stress.