Transcriptional regulation of flavonoid biosynthesis in Artemisia annua by AaYABBY5

Artemisia annua is a medicinal plant rich in terpenes and flavonoids with useful biological activities such as antioxidant,anticancer,and antimalarial activities.The transcriptional regulation of flavonoid biosynthesis in A.annua has not been well-studied.In this study,we identified a YABBY family transcription factor,AaYABBY5,as a positive regulator of anthocyanin and total flavonoid contents in A.annua.AaYABBY5 was selected based on its similar expression pattern to the phenylalanine ammonia lyase(PAL),chalcone synthase(CHS),chalcone isomerase(CHI),and flavonol synthase(FLS)genes.A transient dual-luciferase assay in Nicotiana bethamiana with the AaYABBY5 effector showed a significant increase in the activity of the downstream LUC gene,with reporters AaPAL,AaCHS,AaCHI,and AaUFGT.The yeast one-hybrid system further confirmed the direct activation of these promoters by AaYABBY5.Gene expression analysis of stably transformed AaYABBY5 overexpression,AaYABBY5 antisense,and control plants revealed a significant increase in the expression of AaPAL,AaCHS,AaCHI,AaFLS,AaFSII,AaLDOX,and AaUFGT in AaYABBY5 overexpression plants.Moreover,their total flavonoid content and anthocyanin content were also found to increase.AaYABBY5 antisense plants showed a significant decrease in the expression of flavonoid biosynthetic genes,as well as a decrease in anthocyanin and total flavonoid contents.In addition,phenotypic analysis revealed deep purple-pigmented stems,an increase in the leaf lamina size,and higher trichome densities in AaYABBY5 overexpression plants.Together,these data proved that AaYABBY5 is a positive regulator of flavonoid biosynthesis in A.annua.Our study provides candidate transcription factors for the improvement of flavonoid concentrations in A.annua and can be further extended to elucidate its mechanism of regulating trichome development.

Diversity and versatile functions of metallothioneins produced by plants:A review

Metal ions are essential for plant growth and development,but in excess,these compounds can become highly toxic.Plants have adopted numerous ways to maintain metal homeostasis while mitigating adverse effects of excess metal ions,including phytochelatin and the metal-chelating proteins metallothioneins(MTs).A family of cysteine(Cys)-rich,intracellular,and low-molecular-weight(4-8 kDa)MTs are proteins found in nearly all phyla including plants,animals,and fungi,and they have the potential to scavenge reactive oxygen species and detoxify toxic metals including copper,cadmium,and zinc.Based on their Cys numbers and residues,MTs have been categorized into three major classes.Class I MTs,which have highly conserved Cys residues,are found in animals,while class II MTs,with less conserved Cys residues,are present in plants and are classified further into four groups.Class III MTs include phytochelatins,a group of enzymatically synthesized Cys-rich proteins.The MTs have been an area of interest for five decades with extensive studies,which have been facilitated by advancements in instrumental techniques,protein science,and molecular biology tools.Here,we reviewed current advances in our understanding of the regulation of MT biosynthesis,their expression,and their potential roles in the alleviation of abiotic stresses(i.e.,drought,salinity,and oxidative stresses)and heavy metal detoxification and homeostasis.