Effects Of Light And Hormones On Plant Height Of Peach Trees And Functional Verification Of PpPRE Gene Regulation On Plant Height

Peach（Prunus persica L.）belongs to the Prunus genus and is a member of the Rosaceae family.It is one of the important fruit trees originated in China.The scale of peach cultivation in China has been increasing theses years.In 2022,the cultivated area and the yield of peach werer reached to 867,000 hectares and 16.634 million tons,respectively.However,the peach industry also faces a series of problems.The annual branches of peach grow vigorously and rapidly in summer,and need to be pruned frequently,which resulted to a high labor cost in peach production.Therefore,it is particularly important to study the factors affecting plant height of peach trees.In addition,previous studies have suggested that PRE gene is involved in regulating the elongation and growth of Arabidopsis thaliana,and then affects the plant height.However,whether PRE gene in peach is involved in the regulation of peach plant height has not been verified.In this study,the effects of light and exogenous hormones（GA₃ and BRZ）on the internode length and plant height of peach seedlings were analyzed.Meanwhile,PpPRE genes in peach were identified through peach genome database,and their transcription levels and subcellular localization in different tissue sites were analyzed.The PpPRE1 gene with the highest overall expression was selected for further functional analysis by overexpressing Arabidopsis thaliana.The regulatory relationship between PpPRE1 and genes related to BR synthesis was analyzed by transient peach leaves.The main results are as follows:1.Peach seedlings were treated with different light quality and intensity.The results showed that red light,far red light and weak light could significantly promote the growth of internode length and plant height of peach seedlings.2.When peach seedlings were treated with exogenous hormones（GA₃ and BR）,GA₃ could significantly promote the increase of plant height,while PBZ treatment inhibited the plant height of peach seedlings.The promoting effect of GA₃ on plant height was inhibited when GA₃ and BRZ were applied at the same time.In addition,GA₃ treatment could significantly promote the growth of lateral branch cells,and then promote the plant height.3.According to the information of PREs family genes in Arabidopsis thaliana,four PRE genes were identified in peach genome.Sequence analysis showed that all four PpPRE proteins contained a conserved HLH domain,which was highly homologous to PRE protein in Arabidopsis thaliana.The results of subcellular localization showed that the four PRE genes were located in the nucleus and cytoplasm.4.q RT-PCR was used to analyze the transcription levels of PpPRE genes in different tissue parts and different internode parts.It was found that the transcription levels of four PpPRE genes in young leaves,flower buds and young fruits were significantly higher than those in mature leaves,blooming flowers and mature fruits,and the expression levels of PpPRE genes were higher in stem tips.5.The PpPRE1 overexpression vector was constructed and three PpPRE1 overexpression lines were obtained by Agrobacterium tumefaciens-mediated transformation of Arabidopsis thaliana.Compared to wild-type Arabidopsis thaliana,the three overexpressed lines had higher germination potential,and their hypocotyl and plant height increased significantly.Paraffin sections showed that the cells of the plants overexpressing PpPRE1 were significantly larger than those of the wild type.In addition,the plants overexpressing PpPRE1 had more rosette branches.These results show that PpPRE1 plays an active role in promoting plant height and growth.6.The regulation of PpPRE1 on the transcriptional level of genes related to BR synthesis was analyzed by transient transformation of peach leaves.After overexpression of PpPRE1 in peach leaves,the transcriptional level of genes related to BR synthesis increased significantly.These results suggest that PpPRE1 may regulate the vigorous growth of peach shoots by influencing BR biosynthesis.Taken together,light,exogenous hormones and PpPRE1 genes can regulate plant height,and the promoting effect of PpPRE1 on plant height is related to the transcription of genes related to BR synthesis.This study mainly discussed the effects of different light conditions and hormone treatments on plant height of peach seedlings,preliminarily clarified the regulatory function of PpPRE1 on plant height.The results provide a theoretical basis for breeding excellent peach varieties with suitable plant height.