The Research On The Relationship Between Selected Expression Of Appple Tubulin Family Genes And Apple Dwarfism

China ranks the first in the world with its largest planting area and total production and has been the largest apple producer.However,most of the apple trees in China are cultivated in arboreal or arboreal dense planting,which generally have problems such as large canopy,difficult cultivation and management,strong tree potential,poor canopy,poor ventilation and light penetration,poor fruit quality and low economic efficiency.In contrast,dwarf-dense apple cultivation has the advantages of early fruiting,early yield,good quality,easy management and fast variety renewal,and has now become the mainstream cultivation method in apple orchards.The main measure to achieve dwarf-dense planting is the use of dwarf rootstocks or dwarf varieties as well as short branching genotypes.The probelm is that,according to statistics,in 2019 the area of dwarf dense planting in China only accounted for about 12%of the total cultivated area.In addition to the reasons for low orchard mechanisation and backward cultivation and management techniques,the improper selection of dwarf rootstocks,the shortage of dwarf rootstock resources and the lack of dwarf rootstocks that are compatible with the climate,soil,ecology and main planting varieties of the main planting producing areas are important factors limiting the development of dwarf dense planting in China.Therefore,there is a need to comprehensively analyse the mechanism of dwarfism in apples and to screen for genes regulating dwarfism in apples.The arrangement of microtubules,which can change cell elongation and division in a directional manner,is one of the most direct and important ways to achieve dwarfism in plants.Research on dwarfism in apples is now mainly focused on hormones while the relationship between microtubules and dwarfism has rarely been reported.In the present study,the apple tubulin family genes were firstly identified from the columnar apple ’Runtai’ by bioinformatics,followed by the analysis of tissue-specific expression and post-translational modification processes detected with specific monoclonal antibodies.Moreover,the dwarf rootstock ’T337 ’ and the non-dwarf rootstock Malus.hupehensis were used as the material to investigate the relationship between the selective expression of tubulin genes in dwarf and non-dwarf rootstocks.The main findings were as follows:1.From the apple genome GDDH13V1.1,9 apple α-tubulin sequences and 13 appleβ-tubulin sequences were identified,and the results of multiple sequence alignment revealed that both apple α-tubulin and β-tubulin were highly conserved in the N-terminal amino acid sequence,while the C-terminal end was variable.2.Apple α-and β-tubulin genes TUA3 and TUB3 were highly expressed in all tested tissues of Columnar apple ’Runta’.By using specific antibodies,Western Blot results showed that three types of post-translational modifications,namely tyrosinated tubulin,detyrosinated tubulin and β-tubulin,were commonly found in apple phloem,xylem,leaflet and stem tips.3.In apple xylem,the relative expression of apple genes TUA3 and TUB4 was highest in the non-dwarf rootstock M.hupehensis;in apple phloem,the relative expression of apple genes TUA3 was highest in the non-dwarf rootstock Malus.hupehensis,and the expression of apple genes TUB3 and TUB9 was highest in the dwarf rootstock ’T337’,in apple mature leaf,apple tubulin genes TUA8 and TUB8 were highest expressed in the dwarf rootstock T337;TUA8 and TUB8 were the most expressed in the dwarf rootstock T337;in the young leaves,apple tubulin genes TUA8 and TUB7 were the most expressed in the dwarf rootstock ’T337’;in the apple stem tip,apple genes TUA8 and TUB2 were the most expressed in the dwarf rootstock T337’;in the apple roots,apple genes TUA8 and TUB 10 were the most expressed in the dwarf rootstock T337.The apple root had the highest relative expression of apple genes TUA8 and TUB 10.The current comprehensively study of the apple tu bulin genes provides a theoretical basis for further investigation of mechnism of selected expression of tubulin genes in regulating dwarfism in woody plants.