Research On Gene Expression And Regulation Of Populus Adventitious Root Development

Rooting ability was one of the target traits in Populus genetic improvement. Therefore, it has important significance in both theory and practice to research on molecular mechanism of adventitious root development for Populus. As adventitious root development in cuttings is a highly complex biological progress, in this study, Affymetrix poplar whole-genome array was used to elucidate molecular biological events of adventitious root development of hardwood cuttings from a hybrid Populus clone of Populus×euramericana cv.'Nanlin895', and some related genes were cloned and identified. In addition, expression QTLs analysis based on genetical genomics explored the relationship between gene expression regulation and rooting traits of Populus hardwood cuttings. The main results were as follows:Fifteen GeneChip? poplar whole-genome arrays were used to monitor gene expression profiles during adventitious development stages of hardwood cuttings, and then 14630 significant differently expressed genes were identified at five different developmental stages according to Mulclass SAM comparison.To confirm gene expression data of poplar arrays, thirty-three of 14630 differential expressed genes were verified by quantitative real-time RT-PCR. The results suggested that the poplar array experimental method for adventitious root development was feasible and credible.Integrating molecular biology resources to annotate poplar genome arrays in various biological contexts, furthermore, parts of these differential expressed genes were enumerated. Undoubtedly, the outcome would contribute new ideas on the study of molecular mechanism for adventitious root development in Populus hardwood cuttings.Based on the results above, ten full-length cDNA of genes possibly related to adventitious root development were cloned from emerging roots of cuttings, and the corresponding promoter of PeAux/IAA2 gene was obtained. Moreover, sequence analysis indicted their potential biological function in rooting of cuttings.Plant expression vectors for eight genes of PeAux/IAA1,PeAux/IAA2,PeAux/IAA3,PeAux/IAA4,PeABP1,PeRHD3₁,PeRHD3₂,PeRHD3₃ and one promoter PeAux/IAA2 were constructed and used for Agrobacterium-mediate transformation of Arabidopsis thaliana,Populus×euramericana cv-'Nanlin895 and Populus tremula×Populus tremuloides Michx-clone T89). Some transgenic plants were obtained and further phenotypic identified.Finally, the molecular mechanism on adventitious root development of Populus hardwood cuttings was outlined base on the results of functional mapping and eQTLs analysis of these associated QTLs.