Abstract
Fruit softening is an integral component of ripening and involves the disassembly of wall components by various enzymes. Excessive softening results in large scale post-harvest losses of commercial fruits. We had previously identified SlDREB3 as an activator that reduced ABA levels and responses, leading to early seed germination and delayed fruit ripening/softening when expressed constitutively. Surprisingly, constitutive expression of SlDREB3 also affected seedling establishment causing yellowing and death of almost 50% of the seedlings, besides reducing growth of the surviving plants and imparting drought susceptibility. To overcome this problem, SlDREB3 was expressed under the fruit-specific 2A11 promoter. Expression of pSl2A11::SlDREB3 in transgenic tomato plants eliminated the germination and vegetative growth defects of constitutive expression. All transgenic lines showed normal germination and normal vegetative growth. Reproductive stage effects of SlDREB3 action were enhanced with ripening being delayed by six days in pSl2A11::SlDREB3 fruits and associated with delayed/reduced expression of most genes governing ethylene biosynthesis, ripening regulation and softening. Importantly, post-harvest fruit deterioration, as seen by loss of structure, showed a delay of almost ten days in pSl2A11::SlDREB3 lines over the control. SlDREB3 directly binds the promoter of the ABA degradation gene SlCYP707A3 leading to higher transcript levels that delay ripening. The studies show that the ability of SlDREB3 to delay ripening and softening is enhanced when expressed under the tomato 2A11 promoter compared to the constitutive promoter but associated with none of the vegetative growth defects of constitutive expression. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-025-01676-1.