Analysis Of Farnesoic Acid O-methyl Transferase(FA-O-MeT) Activity And Effect Of Eyestalk Factor On Mandibular Organ(MO) Of Procambarus Clarkii

Decapod crustaceans produce methyl farnesoate(MF) synthesized by the mandibular organ, which is the immediate precursor to the structurally similar insect JH III. Recent studies suggest that MF is involved in the regulation of growth, reproduction, molting, morphogenesis, and behaviour. Farnesoic acid O-methyl transferase (FA-O-MeT) catalyzes the methylation of farnesoic acid (FA) to produce MF in the terminal step of MF synthesis at the existence of S-adenosyl methionine (SAM), and at present it is regarded as a key enzyme in MF biosynthesis pathway.We tested the length, weight and mature index of ovarian at different developmental stages of Procambarus clarkii. And the results showed that the growth and development could be divided into two stages. Before the vitellogenesis stage, the lengths and weights of P, clarkii grow rapidly, while there are almost no changes when the aninal’s ovarian began to develop. The peak occured in the maturity stage and the ovarian index reached3.53%. Based on the statistical data analysis during the different developmental stages of P. clarkii, the relationship between the average length and weight is W=0.0415×L3.1217(r2=0.9762).The activity of FA-O-MeT in crustacean MO was tested by radiochemical assay in three situations (different developmental stages; ESA treatment; SG extract treated after ESA). Our results and analyses suggested that1) there were different FA-O-MeT activities at different developmental stages, the lowest value was at the undevelopmental stage while the peak value at the secondary vitellogenesis stage reached61.75pmol/p/h. However, there was another peak value just before spawning, thereafter it declined immediately. This change might illustrate that the FA-O-MeT or the MF was related to gonad development and spawn behaviour;2) There was no obvious difference in FA-O-MeT activity between the right and the left MO in P. Clakii after analyzing three different developmental stages;3) The FA-O-MeT activity increased rapidly after ESA treatment, and on the fifth day there was a peak then the activity reduced slowly.4) We also used the SG extract to treat MO of both normal and ESA Pclarkii, and FA-O-MeT activity in MO could obviously and dosedepended suppressed by the extract. All of the above showed that FA-O-MeT activity is negatively regulated by eyestalk peptides in SG.In this study, it was found that FA-O-MeT activity in MO is closely related to the development of ovary and is negatively regulated by SG. FA-O-MeT activity also reflects the MF level, so MF was very important in these physiological processes in P.clarkii.