Characterization in maize of ZmTIP2-3, a root-specific tonoplast intrinsic protein exhibiting aquaporin activity

The characterization of the tonoplast intrinsic protein ZmTIP2-3 cDNA isolated from maize roots is reported. ZmTIP2-3 belongs to the TIP2 group according to the present nomenclature. The aquaporin function of ZmTIP2-3 protein was demonstrated using expression in X. laevis oocytes. Northern blot analyses revealed that ZmTIP2-3 was specifically expressed in roots. Salt and water stresses induced the accumulation of ZmTIP2-3 transcripts. By contrast, no effect of ABA was observed. An oscillation of ZmTIP2-3 transcript amount during the day-night cycle was observed with some typical features of genes regulated by a circadian mechanism.