The Function Of PagTAL Involved In Lignin Biosynthesis And Heat Stress Resistance

Transaldolase(TAL)is a key enzyme in the Pentose Phosphate Pathway(PPP).In previous studies,researchers found TAL gene had a certain influence on vascular formation,lignin content and plant stress tolerance in Arabidopsis rhaliana and rice.However,its role in woody plants has not been reported yet.In this study,by using 84K poplar as material,PagTAL1 and PagTAL2 genes were cloned using homologous cloning PCR,and then bioinformatics analysis and tissue specificity analysis were performed.The results showed that PagTAL1 and PagTAL2 were highly homologous to the PtrTALs and the proteins encoded by them were hydrophilic proteins without secretory signal peptides.Subcellular localization predicted that they mainly locate in chloroplasts.Hence,TAL.EGFP vectors were constructed and transient transformed tobacco leaves.Subcellular localization of PagTALs was observed by laser scanning confocal microscope(LSCM).The results showed that PagTAL1 and PagTAL2 were mainly located in chloroplast.Next,enzymatic assay of PagTAL1 and PagTAL2 proteins expressed in prokaryotic system was performed.The results showed that the proteins encoded by these genes had the activity of transaldolase.To further investigate the function of TAL genes,the overexpression of PagTALs materials were generated using the leaf disc transformation method.Then the expressions of PagTAL1,PagTAL1 and the enzymatic activity in 84K poplar wild plants and transgenic plants were analyzed,and the results showed that the expression of TAL genes and the activity of transaldolase in transgenic plants were significantly higher than in 84K poplar wild plants.Phloroglucinol staining was carried out using the transverse section of the 10 th internode stem of PagTAL1 overexpressing plants and 84K wild type poplar plants.It was found that the lignin content of the transverse section of the sten of PagTAL1 overexpressing plants increased compared with 84K wild type plants.Then the expressions of related genes in the lignin synthesis pathway of PagTAL1 overexpressing plants were measured,the results showed that these genes in PagTAL1 overexpressing plants were all significantly higher than that in 84K poplar wild plants.It indicated that PagTAL1 might be invol-ved in the regulation of lignin synthesis.In addition,analysis of the promoters of PtrTALs indicated that there were lots of cis-elements involved in plant stress tolerance in the promoters,such as heat stress responsiveness elements,defense and stress responsiveness elements.To verify the PagTALs regulation of plant stress resistance,the overexpression PagTAL1 plants and 84K poplar wild plants were treated at 40℃ for 96 hours.The MDA level and the enzyme activities of POD and SOD were measured and the results showed that there was a significant difference in MDA content and enzyme activity between the transgenic materials and 84K poplar wild plants after high temperature treatment.It is speculated that PagTAL1 was involved in the regulation of plant resistance to high temperature stress.In summary,using 84K poplar as the experimental material,transaldolase genes PagTAL1 and PagTAL2 were cloned and prokaryotic expression and enzyme activity assay were performed to determine the transaldolase activity of PagTAL1 and PagTAL2.The relative expression and enzyme activity of PagTAL1 in transgenic plants and wild type plants were measured.Then the expressions of related genes in the lignin synthesis pathway were detected,and the changes of MDA content and the relative enzymes activities after high temperature treatment were determined.These results proved that PagTAL1 plays an important role in lignin synthesis and plant resistance to high temperature stress.The results provide a basis for further analysis of the functions of transaldolase in poplar during growth and development.