| Apple(Malus x domestica)as an important fruiter,increasing yield is the key target.Apple branching is the key factor to determine plant type and yield,it is very important to study the ideal type of plants with many branches.The PIN and SMXL family proteins in the model plant of oryza sativa and Arabidopsis thaliana have been systematic identification and expression analysis,and the study shows that PIN and SMXL proteins play a very important role in regulating plant branching.However,the physiological process of apple PIN and SMXL family members involved in the regulation of plant growth is not yet clear,especially the study of MdPIN and MdSMXL regulating the outgrowth of Apple axillary buds has not been reported.In this study,we used apple genome-wide as the template to identify the PIN and the SMXL family members,and the evolutionary relationship,gene structure,cis-element of promoter,conserved domain were predicted and analyzed.To clarify the expression of apple PIN and SMXL family gene in different genotypes and tissues and the expression patterns of related genes after different hormone treatment,and to explore the structural characteristics of apple PIN and SMXL family gene and the mechanism of controlling the outgrowth of apple axillary buds.The main findings are as following:1.Genome-wide identification,phylogeny and expression analysis of PIN family during axillary bud outgrowtht in apple;(1)Identification and annotation of Apple PIN family genes.18 auxin efflux carrier protein pin-formed(PIN)were identified from the Apple genome,they were named according to the order of their chromosomes.(2)Structure and phylogenetic evolution of apple PIN family genes.Apple of PIN gene family structures presents diversity and protein structures were highly conserved.According to apple and Arabidopsis PIN protein evolutionary relationship divided into G1,G2 and G3 subgroup,The evolution of plant PIN proteins was diverse and divergent.(3)Expression analysis of PIN gene family.Apple PIN genes family presented a variety of temporal and spatial expression characteristics in different genotypes of Apple and different apple tissues.The expression of MdPIN15 gene was highest in shoot tip,followed by axillary Bud,and the lowest expression in flower bud.Md PIN genes were rich in a variety of response elements associated with environment and hormones to respond to various responses.Exogenous GR24 and Lovastatin(LVS)treatment decreased the expression of MdPIN15,and suppressed axillary buds outgrowth.while it was increased by exogenous 6-BA and decapitation treatments,and promoted axillary buds outgrowth2.Genome-wide identification,phylogeny and expression analysis of SMXL gene family during axillary bud outgrowtht in apple;(1)Identification and annotation of Apple SMXL family genes.23 SMXL family gene members were identified from the Apple enome,they were named according to the order of their chromosomes.(2)Structure and phylogenetic evolution of apple SMXL genes family.Apple of PIN gene family structures presented diversity and protein structures were highly conserved.SMXL proteins can be divided into G1,G2 and G3 groups according to the evolutionary relationship.The evolution of plant SMXL proteins were diverse and divergent.(3)Expression analysis of PIN gene family.Apple SMXL genes family presented a variety of temporal and spatial expression characteristics in different genotypes of apple and different apple tissues.The expression of most MdSMXL genes in flowers and fruits were higher than eeds and seedlings.MdPIN genes were rich in a variety of response elements associated with environment and hormones to respond to various responses.Exogenous 6-BA increased expression of MdSMXL1,MdSMXL3,MdSMXL4 and MdSMXL11,and promoted axillary buds outgrowth.while them were decreased by exogenous GR24,and suppressed axillary buds outgrowth.3.In this study,a preliminary identification and analysis of two gene families of PIN and SMXL showed that the expression of MdPIN15,MdSMXL1,MdSMXL3,MdSMXL4 and MdSMXL11 increased with axillary bud outgrowth,research showed that these candidate genes were regulating the axillary buds outgrowth.Exogenous Cytokinin promotes the axillary buds outgrowth and induced the expression of these core genes,suggesting that Cytokinin promotes the axillary buds outgrowth possibly by raising these core genes.The GR24 inhibited the axillary buds outgrowth and inhibited the expression of the core genes,indicating that the SL inhibited the axillary buds outgrowth by inhibiting the expression of these core genes.The MdPIN15,MdSMXL1,MdSMXL3,MdSMXL4 and MdSMXL11 of core genes acted downstream of Cytokinin(CK)Auxin(IAA)and Strigolactone(SL)hormones to regulate the apple axillary buds outgrowth. |
