Presence and expression of NAD+-dependent sorbitol dehydrogenase and sorbitol-6-phosphate dehydrogenase genes in strawberry

SummaryThe sorbitol metabolic pathway in strawberry (Fragaria ananassa Duch. var. ‘Nyoho’) is unclear, despite strawberry belonging to the family Rosaceae. Therefore, the presence or absence of genes for NAD+-dependent sorbitol dehydrogenase (NAD-SDH) and sorbitol-6-phosphate dehydrogenase (S6PDH) in strawberry, and their levels of expression related to growth were investigated. A full-length cDNA encoding the NAD-SDH gene in strawberry (FaSDH) was obtained using rapid amplification of cDNA ends (RACE). The full-length clone consisted of 1,399 bp and contained a 1,083 bp open reading frame encoding 361 amino acids with a calculated molecular mass of 38.8 kDa, and a predicted isoelectric point (pI) of 6.08. This nucleotide sequence showed 79 – 85% similarity with the NAD-SDH genes of other plants. Its amino acid sequence contained both zinc- and NAD-binding sites, confirming that this sequence belonged to the NAD-SDH gene family. Southern blotting suggested that the genomic copy number of FaSDH was less th...