Shaoyan Wu

Enhancement of artemisinin content in tetraploid Artemisia annua plants by modulating the expression of genes in artemisinin biosynthetic pathway

Tetraploid Artemisia annua plants were successfully inducted by using colchicine, and their ploidy was confirmed by flow cytometry. Higher stomatal length but lower frequency in tetraploids were revealed and could be considered as indicators of polyploidy. The average level of artemisinin in tetraploids was increased from 39% to 56% than that of the diploids during vegetation period, as detected by high‐performance liquid chromatography–evaporative light scattering detector. Gene expressions of 10 key enzymes related to artemisinin biosynthetic pathway in different ploidy level were analyzed by semiquantitative polymerase chain reaction and significant upregulation of FPS, HMGR, and artemisinin metabolite‐specific Aldh1 genes were revealed in tetraploids. Slight increased expression of ADS was also detected. Our results suggest that higher artemisinin content in tetraploid A. annua may result from the upregulated expression of some key enzyme genes related to artemisinin biosynthetic pathway.

Identification of Putative Artemisia annua ABCG Transporter Unigenes Related to Artemisinin Yield Following Expression Analysis in Different Plant Tissues and in Response to Methyl Jasmonate and Abscisic Acid Treatments

Artemisinin has attracted interest due to its medicinal value in treating malaria and its potential for use against certain cancers and viral diseases. Trichome density and capacity determine artemisinin content in Artemisia annua plants. Thus, the ATP-binding cassette transporter G (ABCG) subfamily involved in trichome cuticle development may also influence artemisinin accumulation. In this study, putative A. annua ABC transporter unigenes were identified and classified from the unigene sequences up to date in the National Center for Biotechnology Information database, and nine putative A. annua ABCG transporter unigenes that may be involved in cuticle development were selected for expression analyses. Two of them, AaABCG6 and AaABCG7, showed parallel expression pattern as two artemisinin biosynthesis-specific genes (amorpha-4, 11-diene synthase and a cytochrome P450-dependent hydroxylase, CYP71AV1) in different tissues and different leaf development stages and also showed similar induction in the plants after methyl jasmonate or abscisic acid treatments. Identification of these putative A. annua ABCG transporter unigenes could provide the basis for cloning of the full-length genes and further functional investigation to find the artemisinin relevant transporters, which could be used for improving artemisinin yield in both A. annua plants and heterologous systems using transgenic technology.

Characterization of a novel ERF transcription factor in Artemisia annua and its induction kinetics after hormones and stress treatments

The full-length cDNA sequence of AaERF3 was cloned and characterized from Artemisia annua. The bioinformatic analysis and phylogenetic tree analysis implied that the AaERF3 encoded a putative protein of 193 amino acids which formed a closely related subgroup with AtERF1, ERF1 and ORA59 in Arabidopsis. The result of subcellular localization showed that AaERF3 targeted to both of the nuclei and the cytoplasm. The qRT-PCR analysis showed that Green young alabastrums had the highest expression level of AaERF3 in the 5-months-old plants. The qRT-PCR analysis also revealed that ABA, Wound and Cold treatments significantly enhanced the transcript expression of AaERF3. MeJA and Ethylene treatment could also slightly induce the accumulation of AaERF3 transcription.