Study On The Regulation Of The Diterpenoid Metabolism By The Rare Earth Element Cerium In Isodon Rubescens

Jiyuan Isodon rubescens were used as the experimental material in this study.The effects of cerium nitrate on the photosynthetic performance and the content of oridonin in I.rubescens were investigated through pot experiment.Isodon rubescens is a special medicinal plant in Henan province.The oridonin of diterpenoids have strong anticancer effects and determine the quality of medicinal herb of Isodon rubescens.The rare earth cerium has various physiological effects on plant growth and development,substance metabolism and material quality.The cuttage was used to study the regulation mechanism of cerium on the metabolism of active components of I.rubescens.The leaf structure,photosynthetic performance,ion group change and RNA sequencing analysis were studied to explore the regulatory mechanism of rare-earth cerium on the growth and metabolism of I.rubescens by solution culture.The results were as follows:1.The experiment of spraying cerium nitrate solution on the potted leaves of I.rubescens and adding cerium nitrate in the culture of nutrient solution showed that a certain concentration of cerium nitrate could significantly improve the concentration of oridonin in the leaves of I.rubescens.In the foliar spraying experiment,300 ?M and 500 ?M cerium nitrate solutions are more suitable,and 10 ?M concentration of nutrient solution is the best.2.The leaves of I.rubescens have the anatomical characteristics of typical dicotyledonous leaves,which are mainly composed of the upper epidermis,palisade tissue,sponge tissue,lower epidermis and vein.The epidermal cells of I.rubescens leaves were irregular,and there were more glandular trichomes and non-glandular trichomes with nodes and cones in the upper and lower epidermis.Stomatal apparatus were mainly distributed in the lower epidermis,and stomatal apparatus types were unequal or irregular.1 ?M and 10 ?M concentration of cerium nutrition significantly promoted the growth of I.rubescens leaves,increased the thickness of palisade tissue and sponge tissue of leaves,and had a greater promotion effect on the growth and development of sponge tissue.Compared with the control group,10 ?M cerium nitrate treated epidermal cells were arranged in a regular manner,which significantly promoted the differentiation of epidermal glandular trichomes on the leaves and significantly increased the number of glandular trichomes,but had no significant influence on the structure of epidermal and glandular trichomes on the leaves.3.Potted I.rubescens leaves sprayed with 300?500 ?M cerium nitrate solution and cultured in nutrient solution with 10 ?M cerium nitrate added significantly increased the chlorophyll content of I.rubescens leaves,enhanced the photosynthetic rate,and increased the biological yield of I.rubescens.4.The addition of 10 ?M cerium nitrate in the nutrient solution promoted the synthesis and accumulation of oridonin mainly by upregulating the transcriptional levels of CPS4 and KSL5 in the downstream of diterpenoid metabolism.The expression level of the isoprene pyrophosphate synthase gene IDI was inhibited to some extent.5.10 ?M of cerium nitrate treatment significantly affected the nutrient levels of various ions from different parts of I.rubescens,significantly improved the ion concentration of Ca and Mg in the roots and the content of Ca and Mg ion in the plant,significantly reduced the ion concentration of Cu,Fe,Mn and zinc in the roots,increased the zinc and Mg ion concentration and content in the leaves,so,cerium nutrition mainly by promoting the absorption of Ca,Mg and keeping higher nutrition level of Mg and zinc in the leaves,so as to promote the photosynthesis of I.rubescens and substance metabolism,and the yield of I.rubescens was increased,the synthesis of oridonin was promoted.6.Transcriptional sequencing analysis of 10 ?M cerium nitrate nutrition revealed a total of 357 differentially expressed genes,among which 164 were up-regulated and 193 were down-regulated.The 66 genes were enriched into 38 KEGG entries,mainly involved in diterpene biosynthesis,pyruvate metabolism,photosynthetic carbon fixation,tricarboxylic acid cycle,oxidative phosphorylation,ion transport and signal transduction.The regulation of cerium nutrients from photosynthetic carbon fixation and respiratory metabolism to pyruvate metabolism provides a substrate for the synthesis of triterpenoids,thus promoting the synthesis of diterpenoids.The results of this study provided an important theoretical basis for the regulation mechanism of rare earth element cerium on the metabolism of I.rubescens,laid a foundation and provided a direction for further research on the regulation mechanism of cerium nitrate on the metabolism and synthesis of active components of I.rubescens,and provided a technical reference for the cultivation,production and management of I.rubescens.