Studies On The Effect Of Components Of Artificial Diet On Gene Expression Efficiency And Recombinant Virus Peroral Infection Of RBmNPV-Bm System

Baculovirus expression vector system is one of the four expression systems in gene engineering field nowadays,and the rBmNPV-Bm expression system is the most promising one in practical application,meanwhile there are still many questions to be solved when it is widely used．First,when medical vaccine and albumen on the medicine are produced in this system,as the host,silkworms must be reared in aseptic condition；second,the recombinant virus is poorly infectious when perorally inoculated the silkworm reared with mulberry leaves,and the method of inj ection is not appropriate for a large scale production because it is time—consuming and labor intensive；third,gene expression were affected by many factors,and the expression efficiency is to be enhanced urgently. In order to promote the foreign gene expression efficiency and increase the peroral infection rate,taking the phytase gene as report gene,the author studied the effects of the components of artificial diet on phytase expression efficiency,and the technique of peroral infection of extracellular virus．The major results obtained in this experiment were as followed,based on the technique of feeding the silkworm with artificial diet． 1．The amounts of mulberry powder,soybean powder,water,vitamin C,vitamin B compound, vitamin B6, inorganic salt in artificial diet had remarkable effect on foreign gene expression efficiency．The difference between the highest activity of phytase and the 10west one iS 1．92 times,1．57 times,3．23 times,2．13 times,2．35 times,4．54 times,1．78 times correspondingly．When the amount of mulberry powder is 1 0％,that of soybean powder 3 5％,water additive amount 1．9 times of dry matter weight, vitamin C l％,vitamin B compound 0．25％,vitamin B6 2megl 00g dry matter weight,inorganic salt 1％,the phytase gene reached its highest expression． 2．The effect of the components of artificial diet on phytase efficiency showed the same tendency as that on body weight．In the treatment the higher is the phytase efficiency,the heavier is the silkworm'S body weight． 3．After a treatment of low temperature(5℃24h)and high temperature(3 8℃1Oh),the peroral infection rate enhanced remarkably．The highest infection rate and the lowest one were 83％and 67％respectively,while the silkworms without any treat was not infected by the virus．After the treatment,the pH ofintestinal j uice dropped down obviously． 4．The effect of optical brightenersVBL and Tinapal LPW on peroralinfection of recombinant virus were studied in detail,and the effect of the concentration of VBL and the method of applying VBL were also disclosed here．The results showed that both the VBL and the Tinapat LPW enhanced the infection effect when perorally inocubated．VBL was prior tO Tinapal, meanwhile it had little influence on the growth and development of silkworms．24 hours after the silkworm ate the diet contained 1％VBL．the recombinantvirus was added tO the diet mixed with 1％VBL．And the rate of infection wasup to 90％．5．When VBL were applied on the diet,the pH value of intestinal juice decreased,and the protease activity dropped down too,and the influence became greater with the concentration increasing．The activity of protease dropped 4．3 1 times after 24 hours when 2％VBL was added into the diet．So it Can be concluded the physiological function and the defensive function of digestive system might be damaged for a short time．Therefore the recombinant virus went across the midgut of silkworms,reached the haemocoele and resulted in the infection．...