Molecular Processes of Dodder Haustorium Formation on Host Plant under Low Red/Far Red (R/FR) Irradiation

Low R/FR irradiation can promote dodder haustorium formation on the host plant; however, the mechanisms underlying the process are still unknown. In this study, we compared the transcriptomic data during the formation of haustorium of Cuscuta chinensis on host plant Arabidopsis thaliana under low (R/FR = 0.1) versus high (R/FR = 0.2) R/FR irradiation at 12 h, 24 h and 72 h time points. The results show that low R/FR radiation significantly promoted the entanglement and haustorium formation. Transcriptome analysis showed that during the early stage of haustorium formation, low R/FR radiation significantly up-regulated ARR-A related genes and down-regulated peroxidase related genes compared with high R/FR radiation. Meanwhile, during the middle stage of haustorium formation, low R/FR treatment significantly increased the expression of genes related to pectinesterase (PE), polygalacturonase (PG) and pectin lyase (Pel) production, while, during the late stage of haustorium formation, peroxidase (Prx)-related genes were differentially expressed under different R/FR treatments. Overall, our findings show that a low R/FR ratio promotes the parasitism of C. chinensis through plant hormone signal transduction and cell wall degradation pathways. This study provides a basis for the control of parasitic plants.