关键词: 甜瓜, 肌醇半乳糖苷合成酶, 基因表达, 遗传转化

Abstract:

Melon belongs to a group of plants that mainly transport Raffinose Family Oligosac- charides（RFOs）. Galactinol synthase（GAS）is the key enzyme of RFOs synthesis. The aim of this study was to explore the function of CmGAS1 in melon. The full-length cDNA of CmGAS1（accession number：AY077642.1）was 1 903 bp，and the open reading frame（ORF）was 996 bp，encoding 331 amino acids. The molecular weight of CmGAS1 protein was about 38 kD，and the theoretical isoelectric point（pI）was 4.81. Amino acid sequence alignment and phylogenetic analysis showed that the amino acid sequences of CmGAS1 had the closest genetic relationship with cucumber（AAO84915.1），and the homology with cucumber was 98.79%. Homology with watermelon（Cla009222）was 97.58%. RT-qPCR analysis showed that the expression of CmGAS1 gene increased significantly from young leaves（sink）to mature leaves（source）. Expression of the fifth leaf reached the maximum value. Compared with the control，gene expression of the fully expanded functional leaves increased distinctly when 50% leaves were removed. The over expression vector of CmGAS1 was constructed with the specific promoter. The genetic transformation of melon was mediated by Agrobacterium. The positive plants were obtained by PCR identification. The net photosynthetic rates，the content of sucrose，raffinose and stachyose all increased in positive plants compared with the wild type. These results suggested that CmGAS1 played an important role in RFOs synthesis in melon leaves.

Key words: melon, galactinol synthase, gene expression, genetic transformation