微囊藻毒素与鱼腥藻毒素对生菜活性氧稳态的复合影响

Compound effects of microcystin and anatoxin on homeostasis of reactive oxygen species in lettuce

水体富营养化导致水体中蓝藻毒素浓度高于安全值.为客观评价灌溉水中蓝藻毒素的生态风险,本研究探析了微囊藻毒素(MCs)和鱼腥藻毒素(ANTXs)对生菜生长和活性氧(ROS)稳态的复合影响.采用5μg·L^(−1)或100μg·L^(−1)MCs、ANTXs和MCs+ANTXs((5+5)μg·L^(−1)或(100+100)μg·L^(−1))处理生菜7 d后发现,低浓度(5μg·L^(−1))MCs、ANTXs或MCs+ANTXs促进生菜鲜重增加63.3%—85.6%,可能是低浓度毒素诱导SOD活性和总抗氧化能力(FRAP)上升以维持H_(2)O_(2)和O_(2)·−平衡进而避免氧化损伤.高浓度(100μg·L^(−1))MCs、ANTXs或MCs+ANTXs抑制生菜生长,降幅为MCs(27.7%)>MCs+ANTXs(16.8%)>ANTXs(5.1%).同时,MDA、H_(2)O_(2)和O_(2)·^(−)含量、NADPH氧化酶活性及LsRbohA表达量、SOD和CAT活性均升高,增幅为MCs>MCs+ANTXs>ANTXs,而FRAP变化不一致.推测高浓度藻毒素上调LsRbohA表达有助于增强NADPH氧化酶活性,生成的ROS增多以刺激防御应激,而SOD和CAT活性上升不足以维持ROS稳定,导致氧化损伤而抑制生长.进一步分析MCs+ANTXs对生菜中ROS稳态复合影响的作用特征发现,MCs+ANTXs(5+5)μg·L^(−1)对MDA、H_(2)O_(2)、NADP氧化酶与CAT活性影响呈现协同效应,在MCs+ANTXs(100+100)μg·L^(−1)处理下呈拮抗效应,表明MCs和ANTXs对生菜ROS稳态的复合影响受毒素浓度的调控,一定浓度的ANTXs共存减轻了MCs对生菜的氧化伤害,为指导灌溉安全提供新的理论依据.

The eutrophication of water leads to the increase of cyanobacteria toxin concentration in water.To objectively evaluate the ecological risk of cyanobacteria toxins in irrigation water,we studied compound effects of microcystin(MCs)and anatoxin(ANTXs)on growth and homeostasis of reactive oxygen species(ROS)in lettuce.After Hydroponic lettuce being treated with MCs(5μg·L^(−1)or 100μg·L^(−1)),ANTXs(5μg·L^(−1)or 100μg·L^(−1))and MCs+ANTXs(5+5)μg·L^(−1)or(100+100)μg·L^(−1)for 7 d,we found that low concentration(5μg·L^(−1))of MCs,ANTXs or MCs+ANTXs increased fresh weight of lettuce by 63.3%—85.6%,indicating that the increase of SOD activity and total antioxidant capacity(FRAP)induced by low concentration of toxin can maintain H_(2)O_(2)and O_(2)·^(−)balance and then avoid oxidative damage.However,high concentration(100μg·L^(−1))of MCs,ANTXs or MCs+ANTXs inhibited lettuce growth,and the decreased degree of each treatment was MCs(27.7%)>MCs+ANTXs(16.8%)>ANTXs(5.1%).Meanwhile,MDA,H_(2)O_(2)and O_(2)·^(−)contents,NADPH oxidase activity and LsRbohA expression,SOD and CAT activities were increased with the order for increased degree as MCs>MCs+ANTXs>ANTXs.In addition,FRAP showed different change among treatments.These results indicate that high concentration treatments up-regulated LsRbohA expression for contributing to enhancing NADPH oxidase activity to produce more ROS for stimulating defense systems.While the increase in SOD and CAT activities was not enough to maintain the stability of ROS,resulting in oxidative damage and inhibition on growth.Furthermore,characteristic analysis of compound effects of MCs+ANTXs on ROS homeostasis in lettuce showed that MCs+ANTXs(5+5)μg·L^(−1)posed synergistic effects on MDA and H_(2)O_(2)contents as well as NADPH oxidase and CAT activities in lettuce whereas MCs+ANTXs(100+100)μg·L^(−1)showed antagonistic effects on them.It can be included that compound effects of MCs and ANTXs on homeostasis of ROS in lettuce was dependent on their concentrations,and the coexistence of ANTXs at a certain concentration could reduce the oxidative damage caused by MCs to lettuce,providing a new theoretical basis for guiding the safety of irrigation water.