| The economic values of the pears depend on the edible quality of the pear fruit. And the stone cell is one of the most factors. So the stone cell of the pear fruit takes the direct effect of the quality. The sediment of lignin comes into being the stone cell.The phenylalanine ammonia- lyase (PAL) which links primary and secondary metabolism by catalyzing the conversion of L-phenylalanine to cinnamic acid, is the first key enzyme in the pathway of plant secondary metabolism. The study which used Yali pear as starting material analyzes the sequence of Yali pear. The major results of this dissertation are as follows:1. High purity RNA was extracted from Yali pear and used as a template for cloning the Phenylalanine Ammonia- Lyase gene cDNA by RT-PCR with specific primers under gradient temperature. Yali pear Phenylalanine Ammonia-Lyase gene cDNA partial sequence was 487 bp long, coding 159 amino acids (accession number: GU355673).2. In the present study, we have amplified the PAL gene fragment using mRNA extracted from the fruit, cloned it in a T-vector, identified by sequencing and further constructed in the plant expression vectors. The analysis showed that the partial sequence, which were 99%, 96%, 87% and 80% homology to that of Pyrus communis, Eriobotrya japonica, Prunus persica, Rubus idaeus PAL cDNA of Genbank, respectively.3. To introduce proper restriction sites for subsequent cloning into the plant expression vector, there was a site for MSEâ… .4. By doing the test of the hydrophobicity the result showed that the amino acids that constitute the Phenylalanine Ammonia-Lyase gene was lyophobic. And the amino acids included the 20 ordinary amino acids. The number between 3 to 11. And the Leu was the most which is 11% and the Pro was laest, 1%. In the 159 amino acids, 64 amino acids of them were lyophobic, which was 40%; 50 amino acids of them were water-loving, which was 34%; 21 amino acids were acidic, which was 12% and 24 amino acids were alkalescent, which was 14%.
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