| The latex produced by rubber trees,known as natural rubber,is an important strategic material and industrial raw material.At present,the continued low price of rubber has seriously affected the sustainable development of the natural rubber industry.Making full use of the undergrowth area of rubber plantations to develop efficient forest economy and improve the output value of rubber plantations is an effective way to solve the sustainable development of rubber industry.Narrow-crown and transparent varieties are suitable plant types for developing understory economy due to their small crown and high light transmittance.The plant type of the aboveground part of the plant is mainly determined by the branch angle,plant height and the space occupied by the leaves.The branch angle is the key factor in determining the plant type.The roles of LAZY and TAC genes in regulating the branching angle have been extensively reported in many plant species.Studies have shown that the expression levels of LAZY in Arabidopsis and tobacco are negatively correlated with their branching angle.Overexpression of the TAC gene in peach trees will increase its branching angle and transform the plant type into a scattered type.Currently,LAZY and TAC family genes have not yet been cloned and functionally studied in rubber trees.In this study,we firstly investigated the plant types of several rubber tree varieties.To explore whether the LAZY and TAC genes have a role in controlling the branching angle of rubber trees,we cloned the LAZY and TAC genes,analyzed the bioinformatics and their expression levels in the terminal buds of several varieties with different branching angles.Additionally,with the aim to improve the plant type of rubber tree by genetic transformation,we carried out a preliminary study on leaf regeneration system and hand-held gene gun transformation system in rubber tree.This study has laid a theoretical and technical basis for understanding the mechanism underlying the regulation of branching angle of rubber trees,and the breeding of rubber trees with improved plant type.The specific results are as follows:1.Through the investigation of the plant types of six rubber tree species,it was found that in the ratio of primary branches to plant height,the two tree types at the young stage were not much different,and there was no obvious difference between the two tree types;but the mature stage Narrow-crown and sparse trees are often larger than branched trees.Regardless of the period,the first-level branch angle of the tree of the same species differs in the range of 0-10°;while the first-level branch angle of the tree of different species differs greatly.2.By q RT-PCR technology,the difference in the expression levels of LAZY gene and TAC gene in the apical buds of different varieties of rubber trees was obtained;with Reyan 73397 as a control,the results showed that the expression level of LAZY gene and TAC gene in the apical buds of Reken 628 and PR107 are much higher than other varieties,combining the plant types of different varieties,it is speculated that LAZY and TAC genes may negatively regulate the branching angle of rubber trees,thereby regulating the plant type of rubber trees.3.Through gene cloning technology,the full-length gene of LAZY3 in the LAZY gene family of rubber tree 73397 variety and the coding sequence of TAC2 in the TAC gene family were obtained,which were defined as HbLAZY3-1 and HbTAC2-1.Compare the obtained two gene sequences with the rubber tree genome and perform bioinformatics analysis on the proteins encoded by the two genes:Obtained that HbLAZY3-1 and HbTAC2-1 have a high similarity with the LAZY3 gene and TAC2 gene sequence in the rubber tree genome,The proteins encoded by both are hydrophilic proteins,and they are mainly composed of random coils and α-helices.Hierarchical structure,no glycosylation site,no transmembrane structure;HbLAZY3-1 is an unstable protein,located in the nucleus,HbTAC2-1 is a stable protein,located in the chloroplast and nucleus.4.During the construction of the leaf regeneration system,the results of different plant hormone concentration combinations on callus induction are obtained.When the three are combined,the best medium formula for inducing green callus is selected as the modified MS medium +0.1 mg/L 6-BA+0.1 mg/L 2,4-D+1.0 mg/L NAA;the green callus in the veins of different explants has the best results.5.In the construction of the gene gun transformation system,the bombardment parameters were optimized,and the transformation efficiency and work efficiency of both benchtop and handheld gene guns were compared.It was shown that the transformation efficiency of both was comparable,but the work efficiency of the handheld gene gun was much higher than that of the benchtop gene gun,which is more suitable for large-scale experiments. |
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