¹³C Stable Isotope Technique To Trace The Metabolic Changes Of Linoleic Acid In The Process Of K. Mikielii

Red tide is a worldwide marine environmental problem.How to find an effective way to prevent the appearance of red tides is a hot spot in the field of marine environmental ecology.The use of large seaweeds to prevent and control the appearance of red tide is an environmentally biological method and this method appears to have certain application prospects.Linoleic acid is a kind of allelochemicals commonly found in large seaweeds,which has a good effect on harmful red tide algae.At present,some work has been done at home and abroad,but it mainly stays at the individual physiological and biochemical level.There is no research on the fate of linoleic acid in the process of the growth of red tide algae in marine environment.Based on this,we focus on the transformation of linoleic acid and the key ingredients derived from it.This study reveals the mechanism of linoleic acid stress Karenia mikimotoi from a new perspective.And the main findings are as follows:(1)The effect of ¹³C linoleic acid on the growth of K.mikimotoiThe effects of ¹³C linoleic acid and linoleic acid on the change of photosynthetic pigment and the growth trend of K.mikimotoi seemed coincident.And the results showed a fat lot difference.To sum up,the existence of isotope hardly shows difference in this experiment.(2)The transformation of linoleic acid under the action of non-biological factors.Linoleic acid mainly appeared in the form of[M+17]and[M+18]after ¹³C linoleic acid was under the action of non-biological factors for 72 hours.And we screened 101 isotopes with a difference of more than 5 times in abundance between the labeled group and the unlabeled group,such as 16-Oxopalmitate(78%),12-OPDA(99%),3-Hydroxy-palmitic acid methyl ester(98%),13(S)-HPOT(92%),2,3-Dinor-8-isoprostaglandin F1alpha(99.9%),9,12,13-Tri HOME(87.6%)and so on.(3)The transformation of linoleic acid in K.mikimotoi cellsAfter ¹³C linoleic acid stressed K.mikimotoi,the isotopes of linoleic acid appeared in the form of[M+2],[M+3];And we found 235 isotopes showed significant differences,of which 62could be mapped to some corresponding pathways,such as Ferroptosis,Porphyrin and chlorophyll metabolism and so on.Those metabolite included multiple Antioxidant substances,such as Astaxanthin,some intermediate products of Ferroptosis and some photosynthetic pigments.(4)Transformation of linoleic acid outside of K.mikimotoiAfter ¹³C linoleic acid stressed K.mikimotoi,the linoleic acid isotope detected outside the cell only appeared in the form of[M+2];114 isotopes showed significant differences,of which35 could be mapped to the corresponding pathways,and 23 isotopes were in both inside and outside of the cell.Pheophytin a and Oligomycin C were detected in outside of the algae and they were not detected under the action of non-biological factors.What's more,the extracellular content of 13 substances(such as Ubiquinone-10)were significantly higher than that under the action of abiotic factors.(5)Changes in the metabolites of K.mikimotoi under linoleic acid stress.Compared with the control group under linoleic acid stress,a total of 12592 differential metabolites were found and 1759 substances could be queried.Among them,94 metabolites were involved in the metabolic pathway(including 33 differential metabolites),44 were involved in the synthesis of secondary metabolites(including 23 differential metabolites);In addition,a variety of significantly different metabolites were involved in porphyrin and Chlorophyll metabolism,carotenoid biosynthesis,steroid biosynthesis,diterpenoid biosynthesis,arachidonic acid metabolism,sphingolipid metabolism,?-linoleic acid metabolism,brassinosteroid synthesis and other metabolic pathways.Results above indicate that ¹³C linoleic acid can be used to study the fate of linoleic acid in K.mikimotoi.Linoleic acid can be detected in both inside and outside of K.mikimotoi,which shows that abiotic factors make little contribution to the degradation of linoleic acid and linoleic acid can participate in the metabolic cycle of K.mikimotoi in the form of degradation product.