The Effect Of Allelochemical Linoleic Acid On The Physiology And Gene Expression Of Chlorella

With the eutrophication of water,the phenomenon that the rapid growing of algae in the water has become serious.The competition between toxic cyanobacteria and eukaryotic algae directly affects the formation of blooms,Studies show that blue algae can become dominant algae in bloom due to linoleic acid?LA?that is the product that can be secreted from Microcystis aeruginosa,and it exhibits allelopathic activity against eukaryotic algae.However,information about the mechanisms associated with the inhibition of algal activity by LA are limited.In this paper,Chlorella pyrenoidosa was used as the experimental object to explore the effect of LA on the growth of Chlorella pyrenoidosa from physiological,biochemical and genetic levels.Linoleic acid?LA?is the product that can be secreted from Microcystis aeruginosa,and it exhibits allelopathic activity against eukaryotic algae.In this study,Chlorella pyrenoidosa was treated with LA(20-120?g·L^-1)for six days,and growth inhibition and physiological responses of C.pyrenoidosa were examined to investigate potential toxic mechanisms.The OD of C.pyrenoidosa significant decreased compared to the controls indicates that LA treatment inhibited its growth.The photosynthetic efficiency of C.pyrenoidosa was inhibited by LA treatments,and the Fv/Fm parameter decreased significantly compared to the controls;however,the photosynthetic pigment content did not change significantly.Peroxidase activity was enhanced,thus relieving oxidative damage in algae after LA treatments.However,superoxide dismutase and catalase were suppressed,ultimately leading to the aggravation of lipid peroxidation.Transcriptome-based gene expression analysis suggested that the 120?g·L^-1 LA treatment significantly inhibited the transcription of genes related to photosynthesis,carbon metabolism,and amino acid metabolism in C.pyrenoidosa,suggesting that these genes represent possible key LA targets in C.pyrenoidosa.Moreover,perturbation of the expression of genes involved in vitamin,lipid,N cycling,terpenoid,and ascorbate metabolism was also observed,suggesting that LA inhibits algal cell growth through multiple pathways.In summary,the growth of C.pyrenoidosa is inhibited and the cell membrane shrinks after treatment with LA.There are many reasons for speculation,such as photosynthesis,enzyme activity,cell structure,and gene level.The identification of LA-responsive genes in C.pyrenoidosa provides new insight into LA stress responses in eukaryotic algae.