Cloning Of Melon’s PDS Gene And Study Of β-Carotenoid Accumulation Molecular Mechanism In Muskmelon

Muskmelon (Cucumis melo L.) is an important horticultural crop in the world. The taste of melon’s fruit is sweet and fragrance, and rich in carotenoids, which the orange-fleshed muskmelon contain large amounts of β-carotene. β-Carotene is one of the most important nutrient elements necessary to the human body, and, as a precursor of vitamin A, β-Carotene can eliminate free radicals, delay aging and prevent cardiovascular disease and cancer. So β-Carotene has a important function of health care and clinical application value. In this research, the full-length cDNA sequence of PDS gene which encodes a key enzyme of carotenoid biosynthesis was cloned by RACE technology, and the accumulation Mechanisms of β-Carotene in orange-fleshed muskmelon Homoken was studied.The main results are as follows:(1) We cloned the full-length cDNA of CmPDS gene from muskmelon inbred line MO1-3using degenerate primers designed according to the conserved sequence of PDS gene from other crops. The full-length of CmPDS’s mRNA was1906bp and contains a1831bp CDS which encoded576amino acids. We have submitted the CmPDS to the GenBank database, and the registration number was KC507802. We found this sequence shares a high conservation with other plant’s PDS genes by sequence alignment, and a trans-membrane region was founded in the104-123(20) of deduced amino acid sequence.(2) We detected the expression pattern of CmPDS using qPCR, and found that CmPDS expressed in muskmelon’s roots, stems, leaves, flowers and fruits, that the expression in green tissue-leaves was highest, and lowest in roots. With fruit’s development, the expression of CmPDS was up-regulated, and reduced in the mature fruits.(3) The trend of determined β-carotene content of fruits to which high performance liquid chromatography was used was similar with expression of CmPDS in orange-fleshed muskmelon Homoken, and was opposite with expression of CmPDS in white-fleshed muskmelon MO1-3in which the β-carotene content reduced in ripened fruit.(4) We mensurated the expression of genes which encodes a enzyme participated in synthesis and decomposition of β-carotene, and found that the expression of synthetic gene PDS and LCY-b in orange-fleshed muskmelon was significantly higher than the white-fleshed muskmelon, and the variation trend of that two gene were similar with β-carotene’s content, while the trend of decomposition gene CCD1was incompatible with which participated in decomposition of β-carotene was incompatible with P-carotene’s content. In white-fleshed muskmelon MO1-3, the variation trend of decomposition gene CCD1was parallel with the PDS’s and LCY-b’s ones. So the interpretation is that the higher synthetic quantity of P-carotene and lower decompositive quantity result in a higher accumulation in orange-fleshed muskmelon.(5) We constructed a CmPDS antisense expression vector, and did some agrobacterium-mediated transformation to muskmelon, and have obtained vitro plantlets.