Molecular Cloning And Analysisi Of A DELLA Gene From Juglans Regia L.

Walnut (Juglans regia L.), the main economic tree in China. The main bole size of walnut is usually from 10 to 25m, its diameter can be about 1m, and diameter of the tree crown is from 6 to 16m. Walnut belong to deciduous arbors and usually applys big crown thinly plants and vigorating compact planting, leading to big tree crown and difficult cultivated management. What is more, the tree crown closure influence the ventilation and lucency, leading to fruit with low quality and low economic returns. Dwarfing culture has lot of advantages, such as fast growth, good quality, convenient management, fast renovation of variety etc. It has become the tendency of fruit industry. In this experiment, the full-length cDNA coding DELLA proteins was got by homologous cloning and RACE technique from‘Liaoning No.2’one of the dwarf walnut species, in order to investigate the dwarf mechanism in molecular level, furthermore, settle the groundwork for the dwarf breeding work. The main results are as follows:1. A 449 bp cDNA fragment was cloned according to conserved sequence of the DELLA homologous genes. It was close to homology gene according to homology analysis and the similarity identity reached 81%. A protein fragment with 149 amino acid residues was deduced, which was 92% and 91% homology to begonia (Genebank:ADH53781)and apple(Genebank:ADH53780)according to BLAST results. It was indicated the correct cDNA fragment was got.2. Then the full-length cDNA was isolated from Liaoning 2 cultivar for the first time based on the fragment. It was 2,361long including 158 bp of 5′UTR, 349 bp of 3′UTR, 12bp of polyA and 1, 842 bp bp of ORF. The gene was named as JrGAI (Genebank:JF766606).3. A 43.15 kDa protein with 613 amino acid residues was deduced according to the JrGAI gene. It was close to the DELLA proteins according to homology analysis and the similarity identity reached 98%. A multiple alignment indicates that the N-termini of these proteins have the two signature motifs,DELLA and TVHYNP, which define the DELLA subfamily and are necessary for GA-induced degradation of DELLA proteins. The C-termini of the DELLA protein have highly conserved motifs (VHVIDand SAW) that are shared by the larger family of GRAS proteins. These domains were the same as the structure of DELLA proteins. So the protein was considered to have the same function as other DELLA proteins.