Abstract
Genomic clones encoding cytosolic triosephosphate isomerase (TPI) and a root-specific gene, and their corresponding cDNA clones have been isolated and characterized from rice. TPI catalyzes the interconversion of dihydroxyacetone phosphate and D-glyceraldehyde-3- phosphate, an essential isomerization reaction in the glycolytic pathway. Using cytosolic TPI cDNA as a probe, it was found that the rice genome contains a single copy of the TPI gene. Northern blot analysis indicates that TPI is expressed in all vegetative tissues and rice suspension calli. Rice cytosolic TPI gene expression in roots and culms can be induced by anaerobiosis but is not light-regulated. The organization of exon-intron boundaries in rice TPI gene is identical to that of maize, and is conserved with that of TPI genes from animals. The coding sequence of the root-specific gene was found to be a member of a small gene family, which shares high sequence homology with a maize cDNA that has been shown to be specifically expressed in young maize roots. The 5' upstream sequences of both the TPI and the root-specific genes were fused to P-glucuronidase (GUS) reporter gene and these chimeric constructs were stably introduced into rice (Oryza sativa L. cv Taipei 309) by protoplast electroporation and into tobacco by Agrobacteriummediated transformation. The 5' upstream sequence of TPI gene can direct high GUS gene expression in transgenic tobacco, whereas in transgenic rice plants, no GUS activity can be detected. Assays of transient expression using microprojectile bombardment also did not give any GUS expression. It is hypothesized that an essential cw-acting element(s) of the TPI gene is required for its expression in transgenic rice. The 5' upstream sequence of the root-specific clone directed high level and cell-specific GUS expression in the roots of a transgenic rice plant. However, high GUS activity was also detected in the leaves of the same plant. These findings indicate that the regulation of root-specificity in rice may be complex and probably involves the participation of sequences other than the 5' flanking region.
Xu, Yong (1993). Isolation and characterization of a triosephosphate isomerase gene and root-specific gene from rice, and analysis of their regulatory sequences in transgenic tobacco and rice. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1522003.