Overexpression of Citrus grandis DREB gene in tomato affects fruit size and accumulation of primary metabolites

Citrus is a perennial woody crop of global economic importance. However, the regulatory mechanism of fruit ripening in citrus remains poorly understood. To explore the regulatory roles of transcription factors in fruit ripening, CgDREB ( d ehydration r esponsive e lement b inding) gene was characterized and was functionally overexpressed in tomato ( Solanum lycopersicum, cv. Ailsa Craig), resulting in smaller fruit size. Therefore, two independent lines with the highest expression of CgDREB were selected to study the metabolite profile in the flesh and peel of tomato fruits during ripening using gas chromatography–mass spectrometry. The results revealed that the levels of organic acids and sugars generally increased in both the flesh and peel of tomato. In addition, a significant increase of ethylene production was observed at the breaker stage, indicating a strong correlation between fruit ripening and ethylene release. Taken together, our results provide insights into the important role of CgDREB gene in regulating fruit ripening properties.