保幼激素拮抗物KK-42对凡纳滨对虾FAMeT时空表达的影响

Effects of juvenile hormone antagonist KK-42 on temporal and spatial expressions of FAMeT in shrimp Penaeus schmitti

保幼激素拮抗物KK-42对凡纳滨对虾(Penaeus schmitti)的生长具有显著的促进作用,并已在大塘养殖中得到推广应用,但其作用机制尚不清楚。为给今后科学合理地使用KK-42提供理论依据,本研究对直接调节甲壳动物生长的重要激素甲基法呢酯(MF)合成的关键酶——法呢酸O-甲基转移酶(FAMeT)的时空表达以及KK-42对其表达的影响进行探讨。将体长3.5～5.0cm凡纳滨对虾幼虾随机分为2组,分别用1.95×10-4mol/L的KK-42溶液或不含KK-42的溶液浸泡处理1min,之后在相同条件下常规饲养。不同组织中FAMeT mRNA水平定量分析采用real-timePCR,血淋巴中MF滴度测定采用正相高效液相色谱法。结果显示,对照组FAMeT在眼柄、肌肉组织中的表达模式与大颚器官明显不同:在实验观察期间,前者组织中 mRNA水平相对较低且变化较小,而在大颚器官则出现明显的波动,第2天、6天、7天、8天FAMeT mRNA含量比第0天均增加1倍以上(P<0.01)。实验期间血淋巴中MF滴度逐渐升高。KK-42处理后,上述3个组织中FAMeT表达均出现不同程度下调,尤以大颚器官最为显著,mRNA水平降低19.7%～63.4%(第8天除外);KK-42处理也导致MF滴度下降。研究表明,KK-42可显著抑制凡纳滨对虾眼柄、肌肉、特别是大颚器官FAMeT转录,降低血淋巴MF滴度,这可能是其促生长的机制之一。

It has been demonstrated that the treatment of juvenile hormone antagonist KK-42 can significantly accelerate growth of Penaeus schmitti,which has been applied in P.schmitti aquaculture,but the mechanism of KK-42 is unclear.To provide the theory support involved in KK-42 application,the temporal and spatial expressions of farnesoic acid O-methyltransferase （FAMeT）,a key synthesis enzyme of methyl farnesoate （MF） which is the important hormone regulating directly crustacean growth,was assayed and the effect of KK-42 on the enzyme was researched.The shrimps （Penaeus schmitti）,3.5 5.0 cm long,were randomly divided into two groups,soaked in KK-42 solution at a concentration of 1.95×10-4 mol/L or in the solution without KK-42 for 1 min,respectively,and then cultured in normal way.The levels of FAMeT mRNA were determined using real-time PCR and hemolymph MF titer was analyzed by normal phase high-performance liquid chromatography.Results showed that the expression pattern of FAMeT derived from the muscle,eyestalk and mandibular organ （MO） tissues varied in control,of which,the mRNA levels in muscle and eyestalk tissues were not only relatively low but also little various during the experiment.However,an obvious fluctuation of mRNA level occurred in MO during the stage of experiment,more than 1-fold of increase in mRNA level was observed on days 2,6,7,and 8 comparing to that on day 0.The hemolymph MF content in control shrimps rose during the experiment.Administration of KK-42 resulted in the universal depression on FAMeT expression in three tissues mentioned above;the most significant inhibitory effect occurred in MO where the level of FAMeT mRNA was considerably lower than that in control group from day 1 to day 7;the level even decreased to 50.9% （P0.01）,63.4% （P0.01） and 55.7% （P0.01） on day1,day 4 and day 6 after KK-42 treatment,respectively.Meanwhile,the amount of hemolymph MF fell in KK-42-treated shrimps compared to that in control ones during the duration of the experiment,which might be involved in famet transcription depression in the animal tissues,especially in the MO.Our present study demonstrates that KK-42 can significantly inhibit FAMeT expression in the MO and muscle as well as eyestalk tissues of the shrimp Penaeus schmitti and decrease the hemolymph MF titer,which may be one of the growth-promoting mechanisms of KK-42 on Penaeus schmitti.