An unconventional road for the secretion of transglutaminase in pollen tubes?

The transglutaminase (TGase) is present in the pollen tube where it most likely participates in the regulation of different activities including the organization of cytoskeletal elements (microtubules and actin filaments). In addition to a cytosolic form of TGase, new data suggest the existence of TGase forms associated with the internal membranes and with the cell wall of pollen tubes. This different localization extends the functional range of pollen TGase but also raises the question how TGase can be precisely (and in harmony with the pollen tube growth) redistributed in different cellular compartments. The discovery that TGase exists as different isoforms may suggest a pathway to achieve this result.