Defining new SNARE functions: the i-SNARE

SNAREs (N-ethylmaleimide-sensitive factor adaptor protein receptors) have been often seen to have a dishomogeneous distribution on membranes and are apparently present in excess of the amount required to assure correct vesicle traffic. It was also shown in few cases that SNARE on the target membrane (t-SNARE) with a fusogenic role, can become non-fusogenic when overexpressed. When SNAREs concentration is inversely proportional to the expected fusogenic activity, they can be reasonably defined as “inhibitory” or “interfering” (i-SNAREs). In fact i-SNAREs have been proposed to form a new functional class of SNAREs. In this manuscript I discuss data obtained in various eukaryotic models that leave open different possibilities for the action mechanism of the i-SNAREs in plants.