The Effect Of KK-42 On Famet Mrna In Mandibular Organ Of Penaeus Schmitti

Methyl farnesoate (MF) is the crustacean homolog of the insect juvenile hormone and is believed to be an important hormone controlling crustacean growth. The crustacean mandibular organ (MO) is the site of synthesis of MF. KK-42 is a kind of juvenile hormone antagonist. Our previous study has demonstrated that the treatment of juvenile hormone antagonist KK-42 can obviously accelerate growth of shrimps (Penaeus schmitti). In attempt to research the possible molecular mechanism of KK-42 growth–promoting effect on Penaeus schmitti, the expression of farnesoic acid O-methyltransferase (FAMeT), a key enzyme of MF synthesis in the MO was assayed.The shrimps, 4.0-5.0 cm long, were soaked for 1 min in KK-42 solution at a concentration of 1.95×10^-4 mol/L, and then cultured in normal way. MOs were collected during the process of cultivation, and hemolymph were collected at different time points. RNA of MOs were extracted using one-step TRIzol with a little modification, and farnesoic acid O-methyltransferase mRNA level was assayed by Real-time PCR. In addition, hemolymph MF titer was determined by high-performance liquid chromatography (HPLC).We have carried out in accordance with the conventional one-step TRIzol to extract RNA , and did not achieve the desired results. In this paper, we appropriately improve the one-step TRIzol and greatly enhanced the RNA yield and quality. In the previous experiments, famet mRNA levels of MOs in the control group were of 86%(P<0.01) and 82%(P<0.01) high respectively, compared with those in KK-42-treated group at 5th and 10th day after treatment. During the post-experiment, the level of FAMeT mRNA in treatment group was considerably lower than that in control MOs from day 1 to day 7, the level even decreased by 50.9% (P<0.01), 37.4% (P<0.01), 63.4% (P<0.01) and 55.7% (P<0.01) on day1, day3, day 4 and day 6 after KK-42 treatment, and also decreased by 22.1 % (P<0.05),35.6 % (P<0.05) and 23.7 % (P<0.05) on day 2, day 5 and day 7 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 experiment, the level decreased by 18.6% and 20.8% on day 4 and day 6 after KK-42 treatment, respectively. Our present study demonstrated that KK-42 could significantly inhibit FAMeT expression in the MO of the shrimp Penaeus schmitti and decrease the hemolymph MF titer.