Cloning And Expression Pattern Analysis Of Nitrogen Starvation-induced Genes In Rice (Oryza Sativa L.)

To understand the regulation system of nitrogen starvation in higher plants, a cDNA library from nitrogen-starved rice (Oryza sativa L.) seedlings was constructed using Rapid Subtraction Hybridization (RaSH) procedure. Through reverse Northern analysis and Northern blotting, 18 unique known genes and 2 unique unknown genes were identified, which were induced by nitrogen starvation in rice. These known genes are involved in (1) carbon metabolism, including starch synthesis, sugar transport, hemicelluloses synthesis and glycolysis; (2) secondary metabolite synthesis; (3) ubiquitylation and protein degradation; (4) plant hormone metabolism, such as ethylene synthesis and auxin transport (5) signal transduction, including the small GTP-binding protein, FKBP12 and ARR6; (6) growth regulator and transcription factor, including 14-3-3 protein, ocs element binding factor(OBF) and KNOX family class 2 homeodomain protein. The result of expression pattern analysis indicated that there were cross-talks between nitrogen starvation response and various metabolisms in plants.A cDNA clone, OsNSIl (Ojyza sfltiva nitrogen starvation- inducible 1) was isolated from this library. The full-length cDNA encodes a protein of 577 amino acids with a predicted molecular weight of 61.2 kD. The deduced amino acid sequence of OsNSIl showed high homology to sugar transporters from other species. Hydropathy analysis revealed that OsNSIl protein composed of 12 transmembrane domains and a central hydrophilic loop. These data strongly suggest that OsNSIl encodes a sugar transporter. Genomic Southern blot analysis showed that OsNSIl might be a single-copy gene in rice genome. Northern blot analysis revealed that OsNSIl was mainly expressed in leaves and roots, and upregulated by N- and P-starvation.