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.

Advances in fungal-assisted phytoremediation of heavy metals:A review

Trace metals such as manganese(Mn),copper(Cu),zinc(Zn),and iron(Fe)are essential for many biological processes in plant life cycles.However,in excess,they can be toxic and disrupt plant growth processes,which is economically undesirable for crop production.For this reason,processes such as homeostasis and transport control of these trace metals are of constant interest to scientists studying heavily contaminated habitats.Phytoremediation is a promising cleanup technology for soils polluted with heavy metals.However,this technique has some disadvantages,such as the slow growth rate of metal-accumulating plant species,low bioavailability of heavy metals,and long duration of remediation.Microbial-assisted phytoremediation is a promising strategy for hyperaccumulating,detoxifying,or remediating soil contaminants.Arbuscular mycorrhizal fungi(AMF)are found in association with almost all plants,contributing to their healthy performance and providing resistance against environmental stresses.They colonize plant roots and extend their hyphae to the rhizosphere region,assisting in mineral nutrient uptake and regulation of heavy metal acquisition.Endophytic fungi exist in every healthy plant tissue and provide enormous services to their host plants,including growth enhancement by nutrient acquisition,detoxification of heavy metals,secondary metabolite regulation,and enhancement of abiotic/biotic stress tolerance.The aim of the present work is to review the recent literature regarding the role of AMF and endophytic fungi in plant heavy metal tolerance in terms of its regulation in highly contaminated conditions.