Molecular basis of differential adventitious rooting competence in poplar genotypes
Résumé
Recalcitrance to adventitious root (AR) development is a major hurdle for propagation of commercially important woody plants. Although significant progress has been made to identify genes involved in subsequent steps of AR development, the molecular basis of recalcitrance to form AR between easy-to-root compaired to difficult-to-root genotypes remain unknown. To address this, we generated cambium tissue specific transcriptomic data from stem cutting of hybrid aspen, T89 (difficult-to-root) and hybrid poplar OP42 (easy-to-root) and used transgenic approaches to verify the role of several transcription factors (TF) in the control of adventitious rooting. Increased peroxidase activity is often positively correlated with better rooting and in agreement, an enrichment of differentially expressed genes encoding Reactive Oxygen Species (ROS) scavenging proteins was observed in OP42 compared to T89. OP42 cambium cells displayed a more intense transcriptional reprograming as highlighted by the higher number of differentially expressed TF compared to T89. PtMYC2, a potential negative regulator, was less expressed in OP42 compared to T89. Using transgenic approaches, we demonstrated that PttARF17.1 and PttMYC2.1 negatively regulate adventitious rooting. These results thus provide insight into molecular basis of genotypic differences in AR and implicate differential expression of master regulator MYC2 as a critical player in this process.