| As one of fruit tree breeding methods, bud sport selection is an important way toimprove the plant-type, coloring and other characterizations, which is good for themodification of varieties composition and upgradation of fruit tree. Because of its excellentplant-type, spur type varieties promotes the dwarf and close planting method, thetransformation of the world apple cultivation system and the efficient development of appleindustry. Therefore, it is necessary to further study the mechanism of spur-type mutantformation, then improve apple varieties and apple industry development.In this study, the shoot internode length, fruit shape index, and plant hormonegibberellins acid of common apple 'Changfu' and its spur type bud sport 'Longfu' have beendetermined; two key genes in gibberellins acid synthesis pathway, GA20ox and KO, wereisolated from 'Longfu' and 'Changfu2', the expression pattern of GA20ox and KO were alsostudied; The suppression subtractive hybridization method have been used to identify thedifferentially expressed genes in 'Longfu' and 'Changfu2'; a gibberellins acid receptor,MdGID1, regulatly the gibberellins acid response, was isolated from 'Longfu', itsexpressionpattern also studied. The main results are as follows:1. The data showed that there was no significant difference between two species in fruitshape index, fruit weight and ratio of sugar to acid during the four stages after flowering.But the obvious difference was found in the internode length. The average length of'Longfu' was2.0cm, which was shorter than that of 'Changfu2' by0.6cm.2. The result of gibberellin (GA) content indicated that in the whole process, the change ofGA content was similar in two materials, namely first increased, then was in a downwardtrend. However, there was a large difference of GA content between two materials at the80-day after flowering. The GA content in the branch of 'Longfu' was110ng·g-1FW.that was in 'Changfu2'249ng·g-1FW, which suggested that the low GA content in'Longfu' caused the spur type phenomenon.3. Based on the homologous clone, the genes of GA20-oxidase and kaurene oxidase wereisolated, which were two key enzymes of GA synthesis pathway. The sequence analysisshowed that there were no mutantion, insertion and deletion in the sequences of two genes between two species. The expression profiles indicated that their expressions wereparalleled with the change of GA content, which caused the GA content difference in twospecies.4. Using suppression subtractive hybridization (SSH) and real-time quantitive PCRtechnologies, it was found that the expression difference of a large number of genesmainly involved in metabolic processes, transcriptional regulation, transportation,photomorphogenesis and stress response.5. By RT-PCE and RACE techniques, a GA receptor, MdGID1was isolated. The sequencephylogenetic analysis indicated that the full-length of MdGID1was1041bp, encoding346amino acids, had identity with GID1in other plants, which suggested it was probablythe GA receptor GID1.6. The upstream sequence of MdGID1was isolated by the High-Tail method. The sequenceanalysis showed there were two exons and one intron in MdGID1. Its upstream sequencecontained several cis-acting elements, including hormones, light and temperature.Real-time quantitive analysis indicated that MdGID1were expressed in all tested tissues,especially high in branch and flower. And its expression was different between twospecies. At the80-day after flowering, its expression was higher in'Changfu2' than thatin 'Longfu' by ten times.7. For the further research of the structure and function of MdGID1and MdRGL, theprokaryotic expression vector pJET-MdGID1and pGEX-4T-MdRGL were constructedand successfully expressed the target protein.
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