Since the discovery of mycorrhizas,dogmas have been developed regarding their function,ecology,and distribution.We explore if these dogmas are valid,and if there are research biases toward regions inhabited by most researchers and away from regions inhabited by most plant species.We found,first,that the mycorrhizal status is known in less than 1%of plant species,with few having proven mycorrhizal benefits for growth and development.Second,the mycorrhizal status of a plant species varies within families,even genera.Third,mycorrhizas are important for phosphorus acquisition only within a narrow phosphorus range.Fourth,mycorrhizal plants are not uniform in their response to environment;taxonomy,phylogeny and continental history strongly drive mycorrhizal diversity.For example,the center of diversification of Ericaceae and Orchidaceae is in the neotropics,rather than,as recently claimed,in cold and high-latitude climates.Understanding the importance of mycorrhizas at the family-wide and biome-wide level is therefore conflicted by a research bias toward research-intensive regions outside the phylogenetic hotspots of diversification.The current precepts on mycorrhizas provide important starting points for hypotheses to robustly test when and where mycorrhizas play a role in determining ecological trajectory.The time has come to move forward and revisit past assumptions and update the dogmas,rather than assume functional significance in terms of nutritional benefits from studies on extraneous regions and species.We conclude that non-nutritional benefits deserve far greater attention.
Paris polyphylla var.yunnanensis is a traditional Chinese medicinal plant,in which polyphyllin as the main medicinal component is an important secondary metabolite with bioactivity.Arbuscular mycorrhizal fungi(AMF)have multiple positive effects on plants,while it is not clear whether AMF increase the content of medicinal components in medicinal plants.In this study,a total of nine AMF treatments were laid to analyze the mycorrhizal effect on polyphyllin accumulation and PpHMGR and PpSE expression of P.polyphylla var.yunnanensis.AMF increased the content of polyphyllin in the cultivated variety with low relation to the increase of inoculation intensity.Polyphyllin I,II,and VII were identified and partly improved by AMF inoculation,dependent on AMF treatments and culture environments.Similarly,the PpHMGR and PpSE expression was induced by mycorrhization,dependent on AMF species,whilst the induction was more obvious in PpSE than in PpHMGR after mycorrhization.It concluded that the symbiotic relationship between P.polyphylla var.yunnanensis and AMF increased polyphyllin content level in the plant,which was associated with the up-regulation of PpSE transcripts.
【目的】从分子水平上对兰科杓兰属大花杓兰根际土壤真菌群落组成及潜在兰科菌根真菌进行初步研究。【方法】采用克隆文库技术对大花杓兰根际土壤真菌的ITS片段进行PCR扩增、克隆测序及BLAST分析。【结果】共获得96个真菌克隆,其中44个克隆鉴定为未知真菌,52个真菌克隆基于97%的序列相似性被划分为24个操作分类单元(Operational Taxonomic Unit, OTU),属于5门6纲11目16科15属。被孢霉属Mortierella为大花杓兰根际土壤的主要真菌类群。综合兰科植物菌根真菌的研究报道,对24个OUTs进一步分析,发现4个OTUs为潜在的兰科菌根真菌,分别属于角担菌科Ceratobasidiaceae的丝核菌属Rhizoctonia(OTU1)和角担菌属Ceratobasidium(OTU2)及胶膜菌科Tulasnellaceae(OTU3和OTU4)。【结论】根际土壤真菌及潜在兰科菌根真菌类群的构成及多样性研究,对从土壤中分离筛选有效的大花杓兰菌根真菌及其野生种群的迁地保育均具有重要意义。
