肉苁蓉（Cistanche Herba）记载于《神农本草经》，是我国传统的可药食两用的中药材，具有补肾阳、益精血、润肠通便的功效。作为全寄生植物，肉苁蓉（Cistanche deserticola Ma）主要寄生在藜科植物梭梭（Haloxylon ammodendron）及四翅滨藜（Atriplex canescens）根部，并通过吸器从寄主植物中获取生长所需的水分及营养物质。肉苁蓉种子吸器形成是寄生过程的关键启动步骤，吸器诱导率可直接关联肉苁蓉接种寄生率。寄生属于生物胁迫，肉苁蓉的寄生会激发寄主植物的防御反应，寄主产生的抗性会导致肉苁蓉出现寄生后消亡、存活率降低的问题，这种防御反应在肉苁蓉寄生早期表现得尤为明显。因此，明确介导吸器发育的化学信号物质，同时揭示寄生建立早期寄主植物的防御调控网络，可为突破肉苁蓉产量低下的技术瓶颈提供关键理论支撑，对实现荒漠药用植物资源可持续利用具有重要实践价值。

通过对比不同季节被寄生及未被寄生的梭梭根代谢组，筛选潜在的吸器诱导物质，并在肉苁蓉种子上进行吸器诱导的验证实验；对肉苁蓉与梭梭、肉苁蓉与四翅滨藜的寄生界面进行石蜡切片显微观察，明确肉苁蓉寄生胁迫对两种不同寄主显微结构影响的异同；结合UPLC-MS/MS技术和RNA-seq技术，对肉苁蓉寄生早期被寄生（Ac）和未被寄生（A）的四翅滨藜根进行分析，通过代谢物参与情况分析四翅滨藜响应寄生胁迫的差异化合物，通过转录组数据分析确定参与四翅滨藜寄生胁迫调控的主要通路；同时通过RNA-seq技术，对变软肉苁蓉寄生的四翅滨藜根（SA）和坏死肉苁蓉寄生的四翅滨藜根（BA）转录组数据进行对比，初步筛选出肉苁蓉寄生早期四翅滨藜应对寄生胁迫的 76 个候选抗性基因，为后续鉴定肉苁蓉寄主植物易感和高抗基因奠定基础。主要研究结果如下：

1.分析不同季节被寄生与未被寄生梭梭根的广靶代谢组数据，发现在梭梭根系检测到的11类物质中，酚酸类代谢物占比最高。结合肉苁蓉吸器诱导相关文献与梭梭根系中差异代谢物的情况，选择2,6-二甲氧基-1,4-苯醌、间苯二酚、阿魏酸、丁香酸、香草酸、香兰素和天竺葵素7种外源信号物质，设置不同浓度检测物质对肉苁蓉种子吸器形成的作用。在7种物质中，丁香酸、香草酸和香兰素能够有效促进肉苁蓉种子吸器形成，其中香草酸促进效果最好，吸器形成率最高能达到50.2%，其次为香兰素和丁香酸。香草酸促进吸器形成的最适浓度为10 μmol/L，香兰素和丁香酸的浓度对促进吸器形成无显著差异。

对肉苁蓉-梭梭寄生体系的寄生点进行石蜡切片，通过染色观察发现被寄生后的梭梭根细胞壁出现增厚现象，其原因是由于肉苁蓉的寄生胁迫导致木质素含量增加，寄生胁迫还导致梭梭细胞壁中的纤维素排列也改变了方向。对肉苁蓉-四翅滨藜寄生体系的寄生点处胼胝质沉积情况进行荧光强度分析，发现肉苁蓉寄生从0.5-2.0 cm（寄生1-2个月）生长至3.0-5.0 cm（寄生3-4个月）过程中，四翅滨藜根的荧光值增加了6.36，四翅滨藜寄生根的胼胝质沉积逐渐增强，推测其在寄生早期对肉苁蓉寄生胁迫的抗性是逐渐递增的。

2.采用UPLC-MS/MS检测的方法，对肉苁蓉寄生早期的四翅滨藜根部代谢物进行检测，检测结果表明，与未被寄生四翅滨藜根相比，被寄生四翅滨藜根中有791种差异代谢物，其中209种代谢物显著上调，582种代谢物显著下调。KEGG通路富集的结果表明，被寄生四翅滨藜根通路主要富集在单萜类生物合成、异黄酮生物合成通路、黄酮和黄酮醇生物合成途径。抗性代谢物可分为：抗氧化物质（如槲皮素）、植保素（如香豆雌酚）和化感物质（如玉米素）。此外，在四翅滨藜寄生根和未被寄生根的差异代谢物里也发现存在阿魏酸、丁香酸以及香草酸这三种物质，与从梭梭代谢组筛选出的吸器诱导物质一致。

3.通过对肉苁蓉寄生前后的四翅滨藜根进行转录组测序，鉴定并注释了寄生后不同寄生结果的差异表达基因：被寄生（Ac）与未被寄生（A）四翅滨藜根的差异基因在GO和KEGG富集分析中显著富集在：植物-病原体相互作用、MAPK信号通路等通路，信号识别相关基因EIX、CEBiP，蛋白激酶EFR和下游转录因子WRKY29表达上调，且MAPK通路中转录因子WRKY22和下游蛋白激酶FRK1表达都上调，表明在肉苁蓉寄生早期，四翅滨藜在对入侵寄生信号后启动了早期防御机制。通过对植物激素信号转导通路进行分析发现，抗性相关激素油菜素内酯、茉莉酸的信号转导基因表达均上调；乙烯的信号转导基因EIN2表达下调，推测是因为在肉苁蓉寄生早期，四翅滨藜对肉苁蓉寄生胁迫的抗性较弱。

4.基于软肉苁蓉寄生（SA）与坏死肉苁蓉寄生（BA）四翅滨藜根的转录组数据，通过对比筛选共上调基因和在BA中特异上调基因，共获得76个抗性候选基因，包括参与逆境胁迫的LRR1、参与细胞形态建成的CPR1及抗病蛋白基因RGA1、RGA2和RGA3。

综上所述，在肉苁蓉的生长发育过程中，吸器发育是寄生关系建立的关键阶段，其诱导机制与寄主释放的外源信号物质密切相关。寄主对寄生植物产生的抗性反应是多种机制的体现，包括自身细胞结构和形态的改变、植保素及化感物质等次生代谢产物特异性积累、植物激素信号通路的调控作用、寄生信号识别与转导系统激活等。通过比较肉苁蓉寄生诱导寄主产生抗性物质的种类，明确寄主植物抗性产生的调控机制；解析肉苁蓉寄生后消亡与寄主植物抗性的关系，为肉苁蓉优良寄主种质筛选和高效栽培提供理论依据和新途径。

Cistanche deserticola Ma, recorded in the Shennong Ben Cao Jing, is a traditional Chinese medicinal material that can be used for medicine and food in China. It tones the liver and kidneys, benefits essence and blood, moistens intestines, and relieves constipation. As an entirely parasitic plant, C. deserticola is parasitic on Haloxylon ammodendron and Atriplex canescens and obtains water and nutrients from the host plants through haustorium. The induction of haustorium in C. deserticola seed is not only a key step in the initial stage of the parasitic process, but also a key factor affecting the parasitic rate. Parasitism is also a kind of biotic stress. Parasitism of C. deserticola will stimulate the host plant's defense response. The host's resistance will lead to a low parasitism rate and low survival rate after successful parasitism. This resistance response is pronounced in the initial stage of parasitism. Therefore, it is urgent to find out the haustorium-inducing substances of C. deserticola and explore the early resistance mechanism of H. ammodendron and A. canescens induced by C. deserticola parasitism, which will help to solve the production problem of low parasitism rate of C. deserticola.

The potential haustorium-inducing substances were screened by comparing the metabolome of the parasitic and non-parasitic H. ammodendron roots, and the validation experiment of haustorium induction was carried out on the seeds of C. deserticola; The parasitic interface between C. deserticola and A. canescens and the parasitic interface between C. deserticola and H. ammodendron were observed by paraffin section to determine the effect of parasitic stress of C. deserticola on the microstructure of the two host cells; With the help of UPLC-MS/MS technology, combined with RNA Seq technology, the parasitic (Ac) and non-parasitic (A) -ms/ms technology, combined with RNA Seq technology, the parasitic (Ac) and non-parasitic (A) A. canescens roots under parasitic stress in the early stage of C. deserticola were analyzed. The differential compounds of A. canescens in response to parasitic stress were analyzed by metabolite participation. The main pathways, which involved in the regulation of parasitic stress, which A. canescens were determined by transcriptome data analysis; At the same time, RNA seq technology was used t to compare the transcriptome data of A. canescens (SA) parasitized by C. deserticola and A. canescens (BA) parasitized by C. deserticola. 76 candidate resistance genes of A. canescens to parasitic stress in the early stage of C. deserticola parasitism were preliminarily screened, which laid a foundation for the subsequent identification of susceptibility and high resistance genes of C. deserticola host plants. The main research results are as follows:

1. Using the UPLC-MS/MS method to detect the root of H. ammodendron, and analyzing the metabolome data of parasitic and non-parasitic H. ammodendron root in different seasons, it was found that among the 11 kinds of substances detected in H. ammodendron root, phenolic acid metabolites accounted for the highest proportion. According to the literature related to haustorium induction of C. deserticola and the situation of differential metabolites in the roots of H. ammodendron, seven exogenous signal substances, 2,6-dimethoxy-1,4-benzoquinone, resorcinol, ferulic acid, syringic acid, vanillic acid, vanillin and pelargonidin, were selected to detect the effects of different concentrations of substances on the formation of haustorium of C. deserticola seeds. Among the seven substances, syringic acid, vanillic acid, and vanillin can effectively promote the haustorium formation of C. deserticola seeds, among which vanillic acid has the best-promoting effect, and the highest haustorium formation rate can reach 50.2%, followed by vanillin and syringic acid. The optimal concentration of vanillic acid to promote haustorium formation was 10 μmol/L, and the concentration of vanillin and syringic acid had no significant difference in promoting haustorium formation.

2. The parasitic spots of the parasitic system of C. deserticola and H. ammodendron were paraffin sectioned. Through staining observation, it was found that the root cell wall of H. ammodendron was thickened after being parasitized. The reason was that the lignin content increased due to the parasitic stress of C. deserticola. This parasitic stress also led to the cellulose arrangement in the cell wall of H. ammodendron, which also changed the direction. According to the fluorescence intensity analysis of callose deposition at the parasitic point of C. deserticola and A. canescens parasitic system, it was found that during the growth of C. deserticola parasitica from 0.5-2.0 cm (parasitic for 1-2 months) to more than 3.0-5.0 cm (parasitic for 3-4 months), the fluorescence value of A. canescens root increased by 6.36, and the callose deposition of the parasitic roots of C. deserticola and A. canescens parasitic system gradually increased, suggesting that its resistance to parasitic stress of C. deserticola is increasing step by step.

3. UPLC-MS/MS technology was used to detect the metabolites of A. canescens root in the early stage of parasitism of C. deserticola: compared with the non-parasitized A. canescens root, the number of differential metabolites in the parasitized A. canescens root was 791, of which 209 metabolites were significantly up-regulated and 582 metabolites were significantly down-regulated. The results of KEGG pathway enrichment showed that the root pathways of A. canescens after parasitization were mainly enriched in monoterpene biosynthesis, isoflavone biosynthesis pathway, and flavone and flavonol biosynthesis pathway. The resistant metabolites of A. canescens, that in response to parasitic stress of C. deserticola can be mainly divided into three categories, including antioxidant substances (such as quercetin), phytoalexins (such as coumestrol) and allelochemicals (such as zeatin). In addition, ferulic acid, butyric acid, and vanillic acid were also found in the differential metabolites of parasitic and nonparasitic roots of A. canescens, consistent with the haustorium-inducing substances screened from the H. ammodendron metabolome.

4. Through transcriptome sequencing of A. canescens roots before and after parasitization of C. deserticola, the differentially expressed genes of different parasitic outcomes after parasitization were identified and annotated: the differentially expressed genes of parasitized (Ac) and non-parasitized (A) A. canescens roots were significantly enriched in plant-pathogen interaction, MAPK signaling pathway and other pathways in GO and KEGG enrichment analysis, and the expression of PRRS genes EIX, CEPiP, LRR receptor-like serine/threonine protein kinase EFR and downstream transcription factor WRKY29 were up-regulated. The expression of transcription factor WRKY22 and downstream protein kinase FRK1 in the MAPK pathway were up-regulated, indicating that A. canescens initiated an early defense mechanism after the signal of invasion parasitism in the early stage of C. deserticola. In addition, phytohormone signal transduction pathways were also significantly enriched. The expression of brassinolide and jasmonic acid signal transduction genes and other genes was up-regulated, but the expression of ethylene signal transduction gene EIN2 was down-regulated. It is presumed that in the early stage of parasitism of C. deserticola, A. canescens has weak resistance to the parasitic stress of C. deserticola.

5. Based on the transcriptome data of soft C. deserticola parasitica (SA) and badly C. deserticola parasitica (BA) A. canescens roots, 76 resistance candidate genes, including LRR1 involved in stress, CPR1 involved in cell morphogenesis, and disease resistance proteins RGA1, RGA2, and RGA3, were obtained through comparative screening of co-upregulated genes and specifically upregulated genes in BA.

In conclusion, haustorium development is a key stage in the establishment of parasitism during the growth and development of C. deserticola, and its induction mechanism is closely related to the exogenous signal substances released by the host. Under parasitic stress conditions of C. deserticola, the host's resistance response is the embodiment of a variety of mechanisms, including the change of its cell structure and morphology, the activation of parasitic signal recognition and transduction system, the specific accumulation of secondary metabolites such as phytoalexins and allelochemicals, and the regulation of plant hormone signaling pathways. Among them, parasitic signal recognition is the key regulatory node to determine the parasitic results, and 76 signal recognition-related resistance candidate genes were screened and obtained in this study. Compare the species of resistance substances induced by C. deserticola parasitism, and clarify the regulatory mechanism of host plant resistance; To analyze the relationship between the demise of C. deserticola after parasitization and the resistance of host plants, and provide a theoretical basis and new ways for the screening of excellent host germplasm and efficient cultivation of C. deserticola.