Isolation and characterization of three maize aquaporin genes, ZmNIP2;1, ZmNIP2;4 and ZmTIP4;4 involved in urea transport

Urea-based nitrogen fertilizer was widely utilized in maizeproduction, but transporters involved in urea uptake, translocationand cellular homeostasis have not been identified.Here, we isolated three maize aquapoin genes, ZmNIP2;1,ZmNIP2;4 and ZmTIP4;4, from a cDNA library by heterogouscomplementation of a urea uptake-defective yeast. ZmNIP2;1and ZmNIP2;4 belonged to the nodulin 26-like intrinsic proteins(NIPs) localized at plasma membrane, and ZmTIP4;4 belongedto the tonoplast intrinsic protein (TIPs) at vacuolarmembrane. Quantitative RT-PCR revealed that ZmNIP2;1 wasexpressed constitutively in various organs while ZmNIP2;4and ZmTIP4;4 transcripts were abundant in reproductive organsand roots. Expression of ZmTIP4;4 was significantly increasedin roots and expanded leaves under nitrogen starvation,while those of ZmNIP2;1 and ZmNIP2;4 remainedunaffected. Functions of maize aquapoin genes in urea transporttogether with their distinct expression manners suggestedthat they might play diverse roles on urea uptake and translocation,or equilibrating urea concentration across tonoplast.[BMB reports 2012; 45(2): 96-101