Medicinal Plant Biology:A new era for medicinal plant research

Plants are amazing chemical factories,and medicinal plants provide a myriad of pharmaceutically active compounds that have been commonly used as traditional medicines for thousands of years.The practice of traditional medicine in China dates back at least 4,500 years.The Shen Nong Ben Cao Jing("Shen Nong's Herbal Classic"in 770−475 BC)has been considered the oldest list of medicinal plants.Recent rapid economic development has enabled China to invest substantially in science and technology research.In many ethnic groups worldwide,herbal medicines are,in the same way as traditional Chinese medicines,still commonly used today.A wide array of plant-extract health supplements has become increasingly popular in Western societies.Numerous drugs derived from a broad range of plant species have been discoveried,such as taxol and artemisinin and their derivatives.

The ERF transcription factor LTF1 activates DIR1 to control stereoselective synthesis of antiviral lignans and stress defense in Isatis indigotica roots

Lignans are a powerful weapon for plants to resist stresses and have diverse bioactive functions to protect human health.Elucidating the mechanisms of stereoselective biosynthesis and response to stresses of lignans is important for the guidance of plant improvement.Here,we identified the complete pathway to stereoselectively synthesize antiviral(-)-lariciresinol glucosides in Isatis indigotica roots,which consists of three-step sequential stereoselective enzymes DIR1/2,PLR,and UGT71B2.DIR1 was further identified as the key gene in respoJanuary 2024nse to stresses and was able to trigger stress defenses by mediating the elevation in lignan content.Mechanistically,the phytohormone-responsive ERF transcription factor LTF1 colocalized with DIR1 in the cell periphery of the vascular regions in mature roots and helped resist biotic and abiotic stresses by directly regulating the expression of DIR1.These systematic results suggest that DIR1 as the first common step of the lignan pathway cooperates with PLR and UGT71B2 to stereoselectively synthesize(-)-lariciresinol derived antiviral lignans in I.indigotica roots and is also a part of the LTF1-mediated regulatory network to resist stresses.In conclusion,the LTF1-DIR1 module is an ideal engineering target to improve plant Defenses while increasing the content of valuable lignans in plants.

植物中松脂醇-落叶松脂素还原酶催化特征研究进展

松脂醇-落叶松脂素还原酶(PLR)是植物中木脂素生物合成的关键酶,能够催化松脂醇转化为落叶松脂素,并进一步催化落叶松脂素生成开环异落叶松脂素,且存在底物立体选择性,是一种NADPH依赖型还原酶。PLR的催化产物位于不同类型8-8′木脂素的源头,其底物选择性直接决定木脂素的骨架类型,如呋喃、二苄基丁烷、二苄基丁内酯和芳基四氢萘木脂素。因此,PLR的催化特性和表达特征在植物木脂素组成及其生物活性多样性中发挥重要作用。该文综述了PLR在植物木脂素生物合成中的作用、对映异构体选择性及其催化机制,以期为进一步研究PLR基因的生物学功能以及催化机制奠定基础,并为不同类型木脂素的精确生物合成指明方向。

Phenotyping of Salvia miltiorrhiza Roots Reveals Associations between Root Traits and Bioactive Components

Plant phenomics aims to perform high-throughput,rapid,and accurate measurement of plant traits,facilitating the identification of desirable traits and optimal genotypes for crop breeding.Salvia miltiorrhiza(Danshen)roots possess remarkable therapeutic effect on cardiovascular diseases,with huge market demands.Although great advances have been made in metabolic studies of the bioactive metabolites,investigation for S.miltiorrhiza roots on other physiological aspects is poor.Here,we developed a framework that utilizes image feature extraction software for in-depth phenotyping of S.miltiorrhiza roots.By employing multiple software programs,S.miltiorrhiza roots were described from 3 aspects:agronomic traits,anatomy traits,and root system architecture.Through K-means clustering based on the diameter ranges of each root branch,all roots were categorized into 3 groups,with primary root-associated key traits.As a proof of concept,we examined the phenotypic components in a series of randomly collected S.miltiorrhiza roots,demonstrating that the total surface of root was the best parameter for the biomass prediction with high linear regression correlation(R^(2)=0.8312),which was sufficient for subsequently estimating the production of bioactive metabolites without content determination.This study provides an important approach for further grading of medicinal materials and breeding practices.

TRICHOMEAND ARTEMISININ REGULATOR 1 Is Required for Trichome Development and Artemisinin Biosynthesis in Artemisia annua

Trichomes, small protrusions on the surface of many plant species, can produce and store various secondary metabolic products. Artemisinin, the most famous and potent medicine for malaria, is synthesized, stored, and secreted by Artemisia annua trichomes. However, the molecular basis regulating the biosynthesis of artemisinin and the development of trichomes in A. annua remains poorly understood. Here, we report that an AP2 transcription factor, TRICHOME AND ARTEMISININ REGULATOR 1 （TAR1）, plays crucial roles in regulating the development of trichomes and the biosynthesis of artemisinin in A. annua. TAR1, which encodes a protein specially located in the nucleus, is mainly expressed in young leaves, flower buds, and some trichomes. In TAR1-RNAi lines, the morphology of trichomes and the composition of cuticular wax were altered, and the artemisinin content was dramatically reduced, which could be significantly increased by TAR1 oeverexpression. Expression levels of several key genes that are involved in artemisinin biosynthesis were altered when TAR1 was silenced or overexpressed. By the electrophoretic mobility shift, yeast one-hybrid and transient transformation β-glucuronidase assays, we showed that ADS and CYP71AV1, two key genes in the biosynthesis pathway of artemisinin, are likely the direct targets of TAR1. Taken together, our results indicate that TAR1 is a key component of the molecular network regulating trichome development and artemisinin biosynthesis in A. annua.

IiWRKY34 positively regulates yield, lignan biosynthesis and stress tolerance in Isatis indigotica

Yield potential,pharmaceutical compounds production and stress tolerance capacity are 3 classes of traits that determine the quality of medicinal plants.The autotetraploid Isatis indigotica has greater yield,higher bioactive lignan accumulation and enhanced stress tolerance compared with its diploid progenitor.Here we show that the transcription factor IiWRKY34,with higher expression levels in tetraploid than in diploid I.indigotica,has large pleiotropic effects on an array of traits,including biomass growth rates,lignan biosynthesis,as well as salt and drought stress tolerance.Integrated analysis of transcriptome and metabolome profiling demonstrated that IiWRKY34 expression had far-reaching consequences on both primary and secondary metabolism,reprograming carbon flux towards phenylpropanoids,such as lignans and flavonoids.Transcript-metabolite correlation analysis was applied to construct the regulatory network of IiWRKY34 for lignan biosynthesis.One candidate target Ii4CL3,a key rate-limiting enzyme of lignan biosynthesis as indicated in our previous study,has been demonstrated to indeed be activated by IiWRKY34.Collectively,the results indicate that the differentially expressed IiWRKY34 has contributed significantly to the polyploidy vigor of I.indigotica,and manipulation of this gene will facilitate comprehensive improvements of I.indigotica herb.

The transcription factors TLR1 and TLR2 negatively regulate trichome density and artemisinin levels in Artemisia annua

The important antimalarial drug artemisinin is biosynthesized and stored in Artemisia annua glandular trichomes and the artemisinin content correlates with trichome density;however,the factors affecting trichome development are largely unknown.Here,we demonstrate that the A.annua R2R3 MYB transcription factor TrichomeLess Regulator 1(TLR1)negatively regulates trichome development.In A.annua,TLR1 overexpression lines had 44.7%–64.0%lower trichome density and 11.5%–49.4%lower artemisinin contents and TLR1-RNAi lines had 33%–93.3%higher trichome density and 32.2%–84.0%higher artemisinin contents compared with non-transgenic controls.TLR1 also negatively regulates the expression of anthocyanin biosynthetic pathway genes in A.annua.When heterologously expressed in Arabidopsis thaliana,TLR1 interacts with GLABROUS3a,positive regulator of trichome development,and represses trichome development.Yeast two-hybrid and pull-down assays indicated that TLR1 interacts with the WUSCHEL homeobox(WOX)protein AaWOX1,which interacts with the LEAFY-like transcription factor TLR2.TLR2 overexpression in Arabidopsis and A.annua showed that TLR2 reduces trichome development by reducing gibberellin levels.Furthermore,artemisinin contents were 19%–43%lower in TLR2-overexpressing A.annua plants compared to controls.These data indicate that TLR1 and TLR2 negatively regulate trichome density by lowering gibberellin levels and may enable approaches to enhance artemisinin yields.

Increased Vitamin C Content Accompanied by an Enhanced Recycling Pathway Confers Oxidative Stress Tolerance in Arabidopsis

Vitamin C （L-ascorbic acid, AsA） has important antioxidant and metabolic functions in both plants and animals. Once used, ascorbic acid can be regenerated from its oxidized form in a reaction catalyzed by dehydroascorbate reductase （DHAR, EC 1.8.5.1）. To analyze the physiological role of DHAR catalyzing the reduction of DHA to ascorbate in environmental stress adaptation, we examined whether increasing the level of AsA through enhanced AsA recycling would limit the deleterious effects of oxidative stress. A chimeric construct consisting of the double CaMV35S promoter fused to the Myc-dhar gene was introduced into Arabidopsis thaliana. Transgenic plants were biochemically characterized and tested for responses to oxidative stress. Western blot indicated that the dhar-transgene was successfully expressed. In homozygous T4 transgenic seedlings, DHAR overexpression was increased up to 1.5 to 5.4 fold, which enhanced foliar ascorbic acid levels 2- to 4.25-fold and ratio of AsA/DHA about 3- to 16-fold relative to wild type. In addition, the level of glutathione, the reductant used by DHAR, also increased as did its redox state. When whole plants were treated with high light and high temperature stress or in vitro leaf discs were subjected to 10μM paraquat, transgenic plants showed a larger AsA pool size, lower membrane damage, and a higher level of chlorophyll compared with controls. These data suggested that increasing the plant vitamin C content through enhanced ascorbate recycling could limit the deleterious effects of environmental oxidative stress.

QUALITY-DESIGN IN TRADITIONAL CHINESE MEDICINE: A CASE STUDY ABOUT ISATIS INDIGOTICA FORT

Quality is the basis for the efficacy of Traditional Chinese Medicine(TCM),affecting herbs,formulations,and even the practice of TCM itself.In our laboratory,we used Isatis indigotica,a prevalent Chinese medicinal herb,as a model to illustrate strategies and methods for TCM Quality-design study.First of all,tetraploid I.indigotica(2n=28)with better yield,higher antiviral activity and enhanced resistance was obtained from its natural diploid progenitor(2n=14)

Isatis indigotica:from(ethno)botany,biochemistry to synthetic biology

Isatis indigotica Fort.(Chinese woad)is a species with an ancient and well-documented history as an indigo dye and medicinal plant.It is often confused with Isatis tinctoria L.(European woad),a medicinal plant in Europe.Here,the differences between I.indigotica and I.tinctoria are systematically described.The usage development history,clinical applications and pharmacological activities,and chemical components of I.indigotica are also summarized.Lignans,indole alkaloids,and their corresponding derivatives have been identified as the major active ingredients of I.indigotica and are associated with anti-viral,anti-inflammatory,anti-cancer,and other health-promoting activities.Notable progress has been made in understanding the biosynthetic pathway and regulation mechanism of lignans and indole alkaloids in I.indigotica,the results from which should facilitate the process of targeted metabolic engineering or synthetic biology.Moreover,multiple biotechnology methods such as polyploid breeding and genetic engineering have been used with I.indigotica to result in,for example,greater yields,higher levels of bioactive component accumulation,and enhanced stress tolerance to salt,drought,and insects.Some issues require additional analyses,and suggestions for future research on I.indigotica are also discussed.