Functional Characterization Of Citrus Grandis DREB(CgDREB) Involved In Fruit Ripening Traits Verified In Transgenic Tomato

Citrus is a perennial woody crop with a world-widely economic importance. However, the regulatory mechanism of fruit ripening in citrus has been less investigated. To explore the regulation role of transcription factors in fruit ripening, CgDREB gene was characterized in Citrus grandis and functionally over-expressed in tomato (Lycopersicon esculentum). Subcellular localization showed that CgDREB protein was localized in the nucleus. Expression patterns of23transgenic lines comparing with wild type were examined by real time-PCR.35S-CgDREBline5,35S-CgDREBlinel5and35S-CgDREBlinel9showed higher expression level among the23transgenic lines. Based on realtime-PCR results,35S-CgDREBline5and35S-CgDREBlinel9lines were used to study the metabolites profile in flesh and peel of tomato fruit during ripening. Primary metabolites in tomato flesh and peel fruits for the transgenic lines and wild type were measured by gas chromatography-mass spectrometry. The levels of organic acids, sugars and fatty acids were dramatically increased in tomato flesh and peel of the two CgDREB lines than wild type. Notable changes of the metabolic profiling response to CgDREB during fruit ripening suggest that CgDREB are involved in fruit ripening regulation. Ethylene production was significantly increased in both CgDREB lines than wild type. A sturdy correlation between fruit ripening and primary metabolite groups, such as organic acids, sugars, and fatty acids and ethylene releasing were observed, which emphasizes the significance of these metabolic changes and ethylene emancipation during fruit ripening. These results shed a new light into the relation between CgDREB and ripening process.