| Endodormancy is an ecological mechanism of perennial deciduous fruit trees in order to withstand cold in winter and external environmental stress.Endodormancy is a complex life metabolism process,including physiological metabolism,hormone response,and regulation of molecular mechanisms.The process of endodormancy of buds has important effects on the growth and development,fruit yield and production distribution of plants.Therefore,understanding the regulating mechanism of bud endodormancy has important theoretical guiding significance for better grasping the flowering and fruiting of fruit tree and improving the yield and quality of fruits.TCP(TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING)transcription factor has the function of regulating plant growth and development.Dormancy-associated MADS-box genes PpDAM5 and PpDAM6 play an important role in the peach bud endodormancy release period.At present,the molecular regulation mechanism of PpDAM5 and PpDAM6 genes in peach is unclear.Recent studies have shown that ABA and GA signal genes(such as ABF,GID1,DELLA)also play an important role in the dormant process.In this experiment,a peach tree bud of ’Zhongyou 4’(Prunus persica var.nectarina)was used as the material,and the mechanism of peach bud endodormancy was explained from the physiological and molecular level.The main findings are as follows:1.During the whole dormant stage,the morphological structure of the ’Zhongyou 4’peach bud did not change significantly.During the endodormancy release stage,the sucrose content of the peach bud reached a peak value of 49.89 mg/g,and subsequently with the release of the endodormancy,the sucrose content decreased;The starch content and related enzyme activities of the peach bud did not change significantly during the entire dormant period.We measured the hormonal content of peach flower bud in different dormant stages and found that the ABA content showed a downward trend during the endodormancy release stage.On January 30,the ABA content was the lowest at 23.36 ng/g.There are three different types of gibberellin in peach buds at different dormant stages,namely GA1,GA3 and GA4.GA1 content is higher than GA3 and GA4.The content of GA1 fluctuated during different dormant stages of flower bud.The content of GA1 increased during the endodormancy stage.On November 15,the content of GA1 was 0.29 ng/g.With the release of endodormancy,the content of GA1 decreased,and the content of GA1 was 0.2 ng/g on December 15.2.There are 20 PpTCP transcription factors in the peach genome,which are named PpTCP1～PpTCP20b.The phylogenetic tree indicates that peach PpTCP transcription factors fall into two families:Class Ⅰ and Class Ⅱ.The Class I family contains 11 PpTCP genes,and the Class Ⅱ is divided into two subfamilies of CIN and CYC/TB1.The CIN subfamily contains 6 PpTCP genes,and the CYC/TB1 family contains 3 PpTCP genes.The PpTCP gene structure and conserved motifs in same family were similar.Colinearity analysis revealed that the amplification of members of the PpTCP transcription factor family in peach mainly came from fragment repeats.Quantitative PCR analysis of the expression pattern of PpTCP gene during the peach flower bud dormancy process,and found that PpTCP2,PpTCP7,PpTCP 10,PpTCP11,PpTCP 14,and PpTCP20 genes were up-regulated during the endodormancy release period.These results suggest that the PpTCP genes may be involved in the endodormancy release of peach buds.3.Yeast one-hybrid experiments showed that PpTCP20 was able to bind to the promoter of the PpDAM6 gene.EMSA experiments show that PpTCP20 binds to the GCCCR cis-acting elements in the promoters of PpDAM5 and PpDAM6 genes;Transient dual luciferase experiments show that PpTCP20 protein inhibits the expression of PpDAM5 and PpDAM6.Subcellular localization indicates that PpTCP20 is a transcription factor localized in the nucleus.Yeast two-hybrid experiments have shown that PpTCP20 protein can form homodimers without active activation.The over-expressed PpTCP20 transgenic tobacco was obtained by Agrobacterium-mediated leaf disc method,and the germination rate of transgenic tobacco seeds was significantly higher than that of the control.In addition,PpTCP20 transgenic tobacco flowered significantly earlier than wild type.We also found that PpTCP20 and PpABF2 proteins can interact to form heterodimers.The expression of PpTCP20 and PpABF2 is up-regulated during the endodormancy release stage to regulate the release of endodormancy.During endodormancy,in vivo and in vitro experiments have demonstrated that the PpTCP20 protein can bind to the promoter of the PpABF2 gene and inhibit its expression.4.The results of yeast two-hybrid experiments showed that PpTCP20 can interact with PpDELLAl and PpDELLA2 proteins.Using different gibberellins to treat peach vegetative bud,it was found that GA3 treatment was more likely to cause peach vegetative buds to fall off.Compared with GA5 treatment,GA4 treatment was more able to promote peach vegetative bud break,and the bud-break rate reached 70%.Moreover,GA4 treatment of peach vegetative buds mainly affected the expression of PpDELLAl and PpDELLA2 genes.It was found that the expression of gibberellin receptor PpGID1C gene was down-regulated during the peach vegetative bud endodormancy release period.The Arabidopsis thaliana overexpressing the PpGID1C gene was obtained by inflorescence infection.Compared to wild-type Arabidopsis seeds,PpGID1c transgenic seeds showed a higher germination rate.In addition,PpGID1c transgenic Arabidopsis thaliana seeds could release PAC from inhibiting seed germination and promote seed germination.The plant height of PpGID1C transgenic Arabidopsis increased,the number of inflorescences and branches increased,and early flowering occurred.Yeast two-hybrid experiments found that PpGID1C protein did not have autonomous activation activity.PpGID1c can interact with PpDELLAl without relying on the presence of gibberellin;PpGID1c and PpDELLA2 interact depend on the presence gibberellin,GA3 and GA4can promote the interaction,and GA5 cannot make PpGID1c and PpDELLA2 interact. |
PDF Full Text Request