Screening And Expression Of The Difference For Gibberellin Related Genes Of Spur-type Apple ’Su Shuai’

Apple(Malus x domestica Borkh.),a woody fruit tree with high economic value in Rosaceae,is one of the most widely cultivated fruits in the world.Taken apple cultivar’Indo’ and ’Golden Delicious’ as female and male parent respectively,the hybrid seeds were obtained.After the hybrid seedlings bear fruits consecutively for 3 years,the hybrids were selected to be an improved strain and named ’Su Shuai’.Compared with its parents,’Su Shuai’ grows vigorously with compact canopy,stout branches,short internodes and deep green leaves.In this study,the contents of endogenous hormones in leaves of ’Su Shuai’,’Golden Delicious’ and ’Indo’ under different treatments were measured;Changes in cells and internodes length of annual stems of ’Su Shuai’ and its parents under different treatments were compared;leaves photosynthetic gas exchange parameters were studied.According to re-sequencing and bioinformatics analysis,18 gibberellin signal transduction and metabolism related genes with non synonymous mutations were selected to be further analyzed.The different expression patterns of those 18 genes in different variety under different treatment were discussed.The main results are as follows:1.The cell length in annual shoot of ’Su Shuai’ was significantly lower than that of’Golden Delicious’ and ’Indo’;The contents of endogenous hormones of ’Su Shuai’ were significant different from that of its parents,including abscisic acid(ABA),gibberellin(GA),indole acetic acid(IAA)and zeatin riboside(ZR).Showed by qRT-PCR results,the expression level of GA2ox8 homologous gene(MDP0000309451)in ’Su Shuai’ was significant higher than that of ’Golden Delicious’ and ’Indo’;while GA3ox4 homologous gene MDP0000196102 was lower expressed in ’Su Shuai’ compared with its parents.MDP0000287040 and MDP0000284679,homologous genes of GRAS domain protein,was higher expressed in ’Su Shuai’ than those in ’Golden Delicious’ and ’Indo’ significantly;and KNOX homologous gene MDP0000166587 was with the similar expression pattern.2.Sprayed with exogenous GA3,the endogenous GA3 content were increased and then decreased;the content of ABA was higher than that of control.GA3 treatment increased the endogenous IAA and zeatin riboside(ZR)content in leaves slightly.By GA3 treatment GA3/ABA,GA3/IAA,GA3/ZR ratio was higher than control.After GA3 treatment,the internodes length of both three varieties was increased.The branches of ’Su Shuai’elongated by 90.05%,which is significantly higher than the 22.50%and 17.90%of ’Indo’and ’Golden Delicious’.GA3 treatment increased stomatal conductance of ’Su Shuai’ leaf,decreased intercellular CO2 concentration and increased the net photosynthetic rate significantly.As for ’Golden Delicious’ and ’Indo’,no significant change of net photosynthesis was observed.The expression level of gibberellin biosynthesis gene MDP0000196102 in ’Su Shuai’ was up-regulated continuously by GA3 treatment,while gibberellin inactivation gene MDP0000309451 was down-regulated.MDP0000287040 and MDP0000284679,which belong to GRAS gene family,were decreased expressed significantly,while the expression level of KNOX homologous gene MDP0000166587 decreased first and then increased.Through single actions or interaction,those five genes may regulate the content of GA3 in ’Su Shuai’,thus result in the tree structure change.3.After PP333 treatment,content of endogenous GA3 in the ’Su Shuai’ leaves was decreased;the ABA content was increased after a first reduction;the IAA and ZR contents were both decreased.GA3/ABA and GA3/ZR ratio was lower than control,while GA3/IAA ratio was higher.Sprayed by PP333,the internodes length of three varieties was decreased by 10.35%,21.37%and 26.44%,respectively.PP333 treatment increased stomatal conductance of ’Su Shuai’,decreased intercellular CO2 concentration as well as transpiration,and increased the net photosynthetic rate significantly;the photosynthetic rate was 110.83%of the control.The expression of gibberellin biosynthesis gene MDP0000196102 in ’Su Shuai’ was up-regulated,while gibberellin inactivation gene MDP0000309451 was down-regulated.The GRAS homologous gene MDP0000284679 was first increased and then decreased,consistent with the change pattern of endogenous gibberellin content in ’Su Shuai’.The results indicated that MDP0000196102,MDP0000309451and MDP0000284679,which homologous to GA3ox4,GA2o8x and GRAS gene family respectively,may play important roles in the mechanism of short internodes phenotype of’Su Shuai’.