Molecular Mechanism Of The Effects Of Typical Polycyclic Aromatic Hydrocarbons On Phospholipid Metabolism In Rice(Oryza Sativa L.)

Phospholipids（PLs）,as an emerging lipid with particular nutritive and physiological functions in crops,have been drawn widespread attention in recent years.Polycyclic aromatic hydrocarbons（PAHs）are ubiquitous pollutants in the environment.The low-ring PAHs are considered to be more easily taken up by crops,which in turn,negatively affecting crops’metabolism and quality.This study selected Oryza sativa L.（O.sativa）as the model organism and compared the accumulated differences of phenanthrene（PHEN）,pyrene（PY）,and benzo[a]pyrene（Ba P）in O.sativa.Moreover,the effects of PHEN,PY,and Ba P on phospholipid content,phospholipase activity and gene expression of phospholipase were discussed.The main results of this paper are as follows:（1）The concentration of PAHs accumulated in rice roots and shoots was PHEN>PY>Ba P,which was negatively correlated with log K_ow.The concentration of the three PAHs accumulated in the roots eventually reached a plateau at an exposure of 400μg/L.Otherwise,the maximum concentration of PHEN,PY,and Ba P accumulated in shoots occurred at exposure levels of 250,10,and 10μg/L,respectively.The accumulation of PHEN,PY,and Ba P in roots was 1.8,6.7 and 12.0 times of that in shoots,respectively.This indicated that the larger the log K_ow of the pollutions,the more difficult it to transport from roots to shoots.However,the phytotoxicity of the three PAHs to rice growth was:PY>PHEN>Ba P,mainly because PY entered the cell and caused severe membrane damage,while Ba P only adsorbed on the cell surface.（2）It was found that PY-exposed groups significantly inhibited the expression of phospholipase coding genes and reduced the contents of typical PLs,thus showing a greater metabolic disturbance than PHEN-and Ba P-exposed groups.Both PHEN-and Ba P-exposed groups increased the expression of phospholipase A₂ and phospholipase C,and the contents of phosphatidylcholine and phosphatidylethanolamine were increased,which promoted the resistance of rice to PAHs.However,the exposure to100μg/L PY resulted in the downregulation of phospholipase A₂ ecoding-genes to 20.7%of the control groups and phospholipase C ecoding-genes to 55.6%of the control groups,resulting in phosphatidylcholine,phosphatidylethanolamine,phosphatidyl-glycerol,and phosphatidylic acid decreased by 89.1%,67.9%,78.3%,and 74.7%,respectively.PY induced severe damage on rice cell membrane,which affected the rice yield and quality.