| Cistanche Herba,the dried fleshy stem of Cistanche deserticola Ma or Cistanche mongolica Beck,is a valuable traditional Chinese medicine native to the northwest desert region of China.C.deserticola is listed in Appendix II of "Convention on International Trade in Endangered Species of Wild Fauna and Flora"(CITES).Such an endangered situation of C.deserticola versus high demand for Cistanche Herba encourages an environment-friendly cultivation method.C.deserticola is a typical Orobanchaceae holo-parasitic plant,which means the host plant influences its quality like abiotic factors(climate,soil,etc.).In recent years,Orobanchaceae parasites have been reported take resistant metabolites from the host plants.Our research on C.mongolica also hinted the influence of host on the quality.When it comes to C.deserticola,the interaction between it and the host plant Haloxylon ammodendron(C.A.Mey.)Bunge remains unclear.The studies on how the host plant influences the quality of C.deserticola are also few.To address the current situation of unstable yield and quality of cultivated C.deserticola,it is necessary to systematically analyze the influence of environmental factors on quality and to clarify the correlation between the accumulation of active ingredients in C.deserticola and its host plants.In this study,88 fresh samples of wild and cultivated C.deserticola samples from 18 distribution sites in Xinjiang were collected in the field to analyze and compare the association between climatic and soil factors and quality traits.Metabolomic and transcriptomic approaches were used to investigate the material and signaling exchanges between C.deserticola and its host H.ammodendron,and to investigate the influence of the host on the accumulation of phenylethanol glycosides in the parasite.The main findings are shown in the following section:1.C.deserticola from different producing areas exihibited variety in the quantification of chemical constituents,and temperature as well as water contributed to such a variety.The contents of 3 phenylethanoid glycosides(echinacoside,acteoside,isoacteoside),ethanol-soluble extractives,polysaccharide and oligosaccharide appeared significantly different according to distribution areas.Samples from the Junggar Basin had the highest contents of phenylethanoid glycosides,while the Tarim Basin-produced C.deserticola contains more carbohydrates.The echinacoside content showed significant positive correlation with the annual precipitation and negative correlation with the average and lowest temperatures in January.The acteoside content negatively correlated with the average temperature in January.A significantly negative correlation appeared between the polysaccharide content and the average/highest temperature in July,while a positive correlation appeared between the polysaccharide and the annual relative humidity.2.The metabolic changes brought about by C.deserticola parasitism were linked to phenylalanine metabolism,tryptophan metabolism,pyruvate metabolism,glycolysis/gluconeogenesis,fructose/mannose metabolism,and propanoate metabolism,which indicates that Haloxylon ammodendron(C.A.Mey.)Bunge makes defensive responses.The main metabolic differences between C.deserticola and its host plant were about phenolic acids.Tyrosol,dopamine,caffeic acid and ferulic acid showed lower contents in C.deserticola.It means that C.deserticola successfully prevented host-derived resistant compounds spreading.In the meantime,phenylethanoid glycosides(Phenylethanoid glycosides,PhG)accumulated in the parasite,which is the result of phenolic acid detoxification.3.In transcriptomic level,the parasitism activated the phenylpropanoid biosynthesis pathway and MAPK signaling pathway.It also induced evident changes in PhG biosynthetic genes such as C4H,4CL,C3H,CCR,and UGT.The result of Pearson’s analysis revealed that their expression levels were evidently correlated with Phenylethanoid glycosides and PhG precursors.It means that H.ammodendron has the capacity of PhG biosynthesis.The large number of UGT85As expressed in C.deserticola highlighted its ability to detoxicate host-derived phenolic acids,which contributes to the accumulation of Phenylethanoid glycosides.Glycosyltransferase genes were upregulated in haustoria.It hints that haustorium takes part in the process of detoxification and helped Phenylethanoid glycosides accumulate in C.deserticola.4.Host dependency influenced the construction of Cytochrome P450 super gene family in C.desertiola.The composition of Cytochrome P450 super gene family showed more similarity to those of Orobanche aegyptiaca Pers.(holoparasite)than Striga hermonthica(Delile)Benth.(Obligate hemiparasite)and Triphysaria versicolor Fisch.&C.A.Mey.(Facultative hemiparasite).Samples were taken from different parts of C.desertiola according to the distance from the host,and the expression of 15 C.desertiola CYP genes including CYP98A and CYP73A,two key enzyme genes for phenylethanoid glycoside biosynthesis,was measured by qRT-PCR method to investigate the effect of host on their expression.The results showed that the expression level of CYP73A,a key enzyme gene for the synthesis of PhG,was lower at the bottom of the stem,but higher in the haustorium connected to the host,and the expression level of CYP98A was higher at the top and bottom of the stem,but lower in the middle and haustorium,so there were site differences in the synthesis of different types of PhGs.In conclusion,this study clarified the influence of environmental factors on the quality of C.deserticola by measuring the differences in the content of active ingredients of samples from different habitats,and the relationship between the accumulation of C.deserticola active ingredients and its host plant by using multiomics analysis.It provides a reference for analyzing the quality formation of C.desertiola,especially those about phenylethanoid glycosides.The results of the study can provide theoretical basis and technical support for the selection of host plants,introduction regional planning and selective breeding of standardization of cultivation of C.deserticola,which is important for the sustainable utilization of the medicinal parasite resources and the stable and controllable quality of the herb. |
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