The cloned tomato anionic peroxidase genes TAP1 and TAP2 correspond to the linked isozymes Prx-2 and Prx-3. Balint-Kurti, P. J. The Sainsbury Laboratory at the John Innes Centre Roberts and Kolattukudy (1989) cloned two highly homologous tomato anionic peroxidase genes, TAP1 and TAP2. These genes were found on the same genomic clone separated by about 1.5 kb. RFLP analysis using pTAP3.7 (a clone carrying the TAP2 gene) identified a Hindlll polymorphism between L. esculentum and L. pennellii DNA. A population of 42 RFLP-characterized L. esculentum x L. pennellii F2 plants provided by Steve Tanksley (Cornell) was then used to map TAP2 (and therefore TAP1) to chromosome 2 (see Figure 1) using the MAPMAKER computer (Lander 1987). This position is very close to that reported for the two anionic peroxidase isozymes Prx-2 and Prx-3 (Tanksley et al. 1993) which are reported to be 0.14 cM from each other (Rick et al. 1979). It is therefore very likely that TAP1 and TAP2 correspond to Prx-2 and Prx-3 although it is not clear which is which. This result also gives some information on the relationship between physical and genetic distance in this region of the genome. It leads to an estimate of 10.7 kb per cM, which is very different to the calculated average for the tomato genome of 750 kb per cM (Tanksley et al. 1993). Near the Tm-2a region, on chromosome 9, 1 cM has been shown to correspond to almost 4 megabases (Ganal et al. 1989) while physical mapping in the L2 region on chromosome 11 has shown that 1 cM corresponds to approximately 43 kb (Segal et al. 1992). It should be emphasized that the genetic distance data used to calculate all these ratios came from separate crosses involving different parents in each case. Literature cited: Ganal, M.W., Young, N.D., and Tanksley, S.D. (1989). Pulsed field gel electrophoresis and physical mapping of large DNA fragments in the Tm-2a region of chromosome 9 in tomato. Molecular General Genetics 215, 395-400. Lander ES, Green P, Abrahamson J, Barlow A, Daly MJ, Lincoln SE, Newburn L: MAPMAKER: An interactive computer package for constructing primary genetic linkage maps of experimental and natural populations. Genomics 1987, 1:174181. Roberts E. -and Kolattukudy P.E. (1989) Molecular cloning, nucleotide sequence and abscisic acid induction of a suberization-associated highly anionic peroxidase. Mol. Gen. Genet. 217:223-232 Rick C.M., Tanksley S.D. and Fobes J.F. (1979) A pseudoduplication in Lycopersicon pimpinellifolium. Proc. Nat. Acad. Sci. USA 76:3435-3439 Segal, G., Sarfatti, M., Schaffer, M.A., Ori, N., Zamir, D., and Fluhr, R. (1992). Correlation of genetic and physical structure in the region surrounding the 12 Fusarium oxysporum resistance locus in tomato. Molecular General Genetics 231, 179-185. Tanksley et al. (1993) High density molecular linkage maps of the tomato and potato genomes. Genetics 132:1141- 1160.

No navigation control above? Click here!