Identification of a new small GTP-binding protein gene OsRab5a, genomic organization, and expression pattern analysis during nitrate supply and early nutrient starvation in rice (Oryza sativa L.) root

A new nitrate-induced gene OsRab5a in rice was isolated using suppression subtractive hybridization (SSH) method. OsRab5a has 1125 nucleotides with an open reading frame of 612 nucleotides encoding a small GTP-binding protein of Rab family. OsRab5a had a higher expression in root, weak expression in shoot, flower and grain, and visually not in stem and leaf. Southern and mapping analysis indicated that OsRab5a would be a single copy gene at locus of 108.8 cM of chromosome 12. Comparison of genomic organization and tissue distribution showed well-conserved genomic organizations and similar expression patterns between OsRab5a gene in rice and Rha1 gene in Arabidopsis during evolution. OsRab5a was quickly induced by nitrate in a split-root treatment, also up-regulated at early nitrogen and phosphorus starvation in root. Acceleration of root growth was observed under nitrate supply, early nitrogen and phosphorous starvation, which was consistent with the expression pattern of OsRab5a. These results suggest that OsRab5a may function in nutrient-regulated root growth. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.