| Root is an important organ of plants adapting to the terrestrial habitat for a long time.The complete plants obtained by adventitious root generation can maintain the excellent characteristics of the mother plant and are widely used in plant cutting and tissue culture.The rooting ability of the clones is the key to the success of poplar cutting propagation and the main criterion to judge the adaptability and stress resistance of the clones.Therefore,rooting characters of cuttings play an important role in tree genetic improvement.Jasmin(JA)is an important plant hormone,plays an important role in plant growth and development,also closely related to the emergency of adventitious roots.Currently,much work has been done on the role of jasmonin in the process of adventitious root formation and its regulation mechanism in Arabidopsis Thaliana,moreover,the regulation effect of jasmin on the emergency of adventitious roots was also found in poplar,a woody model plant.It was found that jasmin inhibited adventitious root formation in Arabidopsis thaliana,but promote the adventitious root of poplar,suggest that jasmin has different functions and regulatory mechanisms between poplar and Arabidopsis,but the molecular regulation mechanism of poplar has not been studied.In this paper,PuMYC2 gene,a key regulator of jasmonic acid signaling pathway in populus grandis was studied,in order to explore the effect of PuMYC2 transcription factor on adventitious root development of Populus ussuriensis.In this article,the full length coding sequence of PuMYC2 gene was cloned and analyzed by bioinformatics,the total length of PuMYC2 gene coding region of Populus ussuriensis was 1476bp,encode protein with 491 amino acid residues,the relative molecular weight was 54710.63,the theoretical isoelectric point is 5.4 which means PuMYC2 belong to acidic protein,the coefficient of instability is 53.39,the average hydrophilicity was-0.485.Evolutionary tree analysis found that PuMYC2 has higher similarity among PtrMYC2 and HbMYC2.The results of domain prediction show that PuMYC2 has conservative bHLH-MYB and HLH domains.The results of qRT-PCR analysis indicated that:at the base of stem segment of tissue culture seedlings of Populus ussuriensis,PuMYC2 was significantly up-regulated during the whole process of adventitious root formation,while jasmin biosynthesis inhibitor salicylhydroxamic acid(SHAM)treatment could significantly inhibit its expression.This indicated that PuMYC2 can be induced by injury and its expression can be regulated by endogenous jasmin.By performing Subcellular localization and transcriptional activation found PuMYC2 is expressed in the nucleus,and it has transcriptional activation activity.To investigate the effect of PuMYC2 transcription factor on the development of adventitious roots in Populus ussuriensis,the pBI 121-PuMYC2-GFP and pBI121-PuMYC2-SRDX vectors were constructed and their genetic transformation of Populus ussuriensis was performed,by comparing the adventitious root rooting characters between transgenic lines and wild type line,we found the number of adventitious roots and the incidence at the same time were significantly higher in PuMYC2 overexpression lines than in wild-type line while PuMYC2 inhibited line was significantly lower than wild-type line,the occurrence time of PuMYC2 overexpression was earlier than that of PuMYC2 inhibited expression,these results prove that PuMYC2 positively regulated adventitious root development of tissue culture seedlings of Populus ussuriensis.Further qRT-PCR analysis revealed that compared with wild type Populus ussuriensis,three of known homologous adventitious root locus regulation genes in Populus ussuriensis,PuGH3.1,PuGH3.5 and PuARF6,were upregulated in PuMYC2 overexpressed lines during adventitious root formation,while expression in PuMYC2 inhibited expression lines were downregulated,it was further proved that PuMYC2 had a positive regulatory effect on adventitious root development of Populus ussuriensis. |
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