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Japanese dodder ( Cuscuta japonica) is a flowering, parasitic weed that causes major yield losses on crop and forest production. In the present field study, the influence of Cuscuta on the growth and secondary metabolite of its host medicinal shrub Madagascar periwinkle ( Catharanthus roseus) was investigated. Vegetative and reproductive growth of the host plant Catharanthus was measured at intervals from 0 to 60 days after inoculation (DAI), and content of three alkaloids, naturally produced by the host, in the host and parasite were measured by HPLC at intervals from 15 to 45 DAI. Dodder infection significantly inhibited biomass accumulation and reproductive growth of Catharanthus, and aerial parts of the host died by 60 DAI. Levels of alkaloids vinblastine, vindoline and catharanthine in the inoculated Catharanthus were lower than in uninoculated control plants, both in immature leaf and in mature leaf, except the alkaloids contents were elevated in host immature leaf compared with uninoculated control plants immature leaf at 15 days. The host plant thus actively responded to dodder infection by accumulating alkaloids acts as a defense molecule at 15 DAI. The alkaloids produced by host plants accumulated in dodder at 15-45 DAI, and the alkaloid content in dodder reached a maximum at 45 DAI. The alkaloids transported from host to parasite act as a sink, the high content of alkaloids in dodder be cytotoxic and accelerated the onset of senescence. [ABSTRACT FROM AUTHOR]

Research on transcriptional regulation of terpenoid indole alkaloid (TIA) biosynthesis of the medicinal plant, Catharanthus roseus, has largely been focused on gene function and not clustering analysis of multiple genes at the transcript level. Here, more than ten key genes encoding key enzyme of alkaloid synthesis in TIA biosynthetic pathways were chosen to investigate the integrative responses to exogenous elicitor ethylene and copper (Cu) at both transcriptional and metabolic levels. The ethylene-induced gene transcripts in leaves and roots, respectively, were subjected to principal component analysis (PCA) and the results showed the overall expression of TIA pathway genes indicated as the Q value followed a standard normal distribution after ethylene treatments. Peak gene expression was at 15-30 μM of ethephon, and the pre-mature leaf had a higher Q value than the immature or mature leaf and root. Treatment with elicitor Cu found that Cu up-regulated overall TIA gene expression more in roots than in leaves. The combined effects of Cu and ethephon on TIA gene expression were stronger than their separate effects. It has been documented that TIA gene expression is tightly regulated by the transcriptional factor (TF) ethylene responsive factor (ERF) and mitogen-activated protein kinase (MAPK) cascade. The loading plot combination with correlation analysis for the genes of C. roseus showed that expression of the MPK gene correlated with strictosidine synthase ( STR) and strictosidine b- d-glucosidase( SGD). In addition, ERF expression correlated with expression of secologanin synthase ( SLS) and tryptophan decarboxylase ( TDC), specifically in roots, whereas MPK and myelocytomatosis oncogene ( MYC) correlated with STR and SGD genes. In conclusion, the ERF regulates the upstream pathway genes in response to heavy metal Cu mainly in C. roseus roots, while the MPK mainly participates in regulating the STR gene in response to ethylene in pre-mature leaf. Interestingly, the change in TIA accumulation does not correlate with expression of the associated genes. Our previous research found significant accumulation of vinblastine in response to high concentration of ethylene and Cu suggesting the involvement of posttranscriptional and posttranslational mechanisms in a spatial and temporal manner. In this study, meta-analysis reveals ERF and MPK form a positive feedback loop connecting two pathways actively involved in response of TIA pathway genes to ethylene and copper in C. roseus. [ABSTRACT FROM AUTHOR]