Plant & Animal Genome VI Conference

P62

PRESENCE OF DI-NUCLEOTIDE REPEATS (CA/GT) IN THE GENE ENCODING SORBITOL-6-PHOSPHATE DEHYDROGENASE IN APPLE: ITS ALLELIC DIVERSITY AND SEQUENCE HOMOLOGIES TO Pyrus AND Prunus SPECIES

Department of Pomology, University of California, Davis, CA 95616

Sorbitol, a sugar alcohol, which is prevalent in various genera and species of the family Rosaceae has been suggested to play an important role in the drought and salt tolerance in plants. We have cloned and characterized the genomic DNA sequence coding for the NADP dependant Sorbitol-6-phosphate dehydrogenase (S6PDH, E.C.1.1.1.200), a primary enzyme involved in the sorbitol synthesis, from the apple cultivar, Greensleeves (Bains et al. submitted). The DNA sequence analysis of this gene revealed the presence of a dinucleotide (CA/GT) simple sequence repeat in the intron-3 region. PCR primers were designed for the conserved exon regions flanking the intron-3 sequence and used in PCR amplification of genomic DNAs from cultivars of apple (Malus sp.), pear (Pyrus sp.) and peach, apricot, cherry, plum and almond (Prunus sp.). The analysis revealed two putative loci for the S6PDH gene, i.e., S6PDH-1 and S6PDH-2 in the apple and pear cultivars, while a single locus that correspond to the S6PDH-1 of the apple was amplified for all diploid members of the Prunus species. Genetic segregation in an F₂ population of a peach x almond cross confirmed the Mendelian nature of the S6PDH-1 locus. The extent of allelic diversity for this gene and its utility in the genome analysis of Malus species is presented.