Transformation of Japanese persimmon (Diospyros kaki Thunb,) with apple cDNA encoding NADP-dependent sorbitol-6-phosphate dehydrogenase

Japanese persimmon (Diospyros kaki Thunb. cv Jiro) was transformed with app le (Malus x domestica Borkh.) cDNA encoding NADP-dependent sorbitol-G-phosp hate dehydrogenase (S6PDH) by an Agrobacterium -mediated leaf-disc transfor mation system. Integration and expression of the transgene were confirmed b y genomic DNA blot and immunoblot analyses. Sorbitol accumulation in five o f six transgenic plants obtained was confirmed by GC-MS. The amount of sorb itol in the leaves of transgenic plants varied from 14.5 to 61.5 mu mol g(- 1) fr wt(-1). Sorbitol was not found in leaves of non-transformed 'Jiro' or the line PS7 that produced S6PDH protein with no S6PDH activity. Eventuall y, two transformed lines producing high (PSI) and medium (PS6) amounts of s orbitol, one control transformed line (PS7), and non-transformed 'Jiro' wer e selected and evaluated for salt-stress tolerance. Under NaCl stress, the activity of photosystem II in leaves was determined in terms of the ratio o f the variable (Fv) to the maximum (Fm) fluorescence of chlorophyll. The ra te of decline in Fv/Fm under NaCl stress was lower in PS1 than the other th ree lines, suggesting that PS1 is more tolerant to NaCl stress than the oth er three lines. The factors that caused enhanced salt stress tolerance in P S1 are discussed in relation to sorbitol biosynthesis and its growth. (C) 2 001 Elsevier Science Ireland Ltd. All rights reserved.