DR tomato line 8338 was developed by introducing into the genome of a processing tomato cultivar UC82B a gene (accd) derived from a nonpathogenic soil bacterium (Pseudomonas chlororaphis) that encodes the enzyme ACCd.  In the plant, this enzyme catalyzes metabolism of 1-amino-cyclopropane-1-arboxylic acid (ACC), an essential precursor for the biosynthesis of the plant hormone ethylene.  <br>The initiation and progression of tomato fruit ripening depends on increased levels of ethylene.  In line 8338, ACC is sufficiently reduced in detached fruit so that ethylene becomes limiting and the ripening process is delayed.  Noncoding DNA sequences that are associated with the introduced accd gene to regulate its expression in line 8338 include the constitutively expressed 35S promoter derived from the plant pathogen figwort mosaic virus, a leader sequence from the petunia HSP70 gene, and the 3' terminator region of a pea ribulose-1,5-bisphosphate carboxylase small subunit gene. <br> Line 8338 has also been transformed with the nptII gene derived from <i>E. coli</i> that encodes the enzyme NPTII.  NPTII confers resistance to certain antibiotics, such as kanamycin, that are used to select transformed cells.<br>Noncoding DNA regulatory sequences associated with the nptII gene comprise the 35S promoter derived from the plant pathogen cauliflower mosaic virus and 3' termination sequences derived from the nopaline synthase gene from the plant pathogen <i>A. tumefaciens</i>.  These two genes were introduced into the tomato cultivar UC82B to create the original (R0) transformed DR line via Agrobacterium-mediated transformation.  This is a well-characterized procedure that has been used widely for over a decade to introduce various genes of interest directly into the plant genome.  The DR tomato line 8338 is actually a homozygous R2 selection from the R0.