Biotransfer And Effect Mechanisms Of Cry1Ab Insecticidal Protein In Rice Plant-Rice Leaf Folder-Apanteles Cypris Nixon Food Chain

Biosafety of transgenic crops has been becoming a focus in the world. Concerns on the biosafety of transgenic rice are necessary, because rice is one of staple foods of human. Biosafety assessments should be systematically and scientifically conducted before the commercialization of transgenic rice. So, a series of laboratory and field experiments were carried out in order to systematically evaluate the biosafety effects of the transgenic rice lines with cry1 Ab gene on both their target and non-target organisms.1 Effects of transgenic Bt rice expressing a gene of cry1Ab on the food consumption, growth and survival of rice leaf-folder larvaeThe transgenic rice KMD1, expressing a synthetic Cry1Ab gene from Bacillus thuringiensis, showed effective resistance to the older (third- to fifth-instar) larvae of the rice leaf-folder (RLF), Cnaphalocrocis medinalis (Guenee) in laboratory bioassay. Significant declines were revealed in food consumption and growth of the older RLF nymphs fed on the cut-leaves of transgenic KMD1 plants. The increase rate of food consumption by larvae fed on KMD1 was drastically lower than those on Xiushui 11. Food consumption was varied with different instars when the larvae fed on the Bt rice. Those of four- and fifth-instar larvae were different compared to the third-instar, lower than those on the non-transgenic rice but still increased a litter when the feeding time prolonged. It is indicated that younger RLF larvae are more sensitive to Bt rice than older ones. Also, about 81%, 78% and 68% of the third-, fourth- and fifth-instar RLF larvae died within 72 hours bioassay period on KMD1 leaves, respectively. These results demonstrated that the transgenic Bt rice "KMD1" confers substantial protection against infestation with older RLF larvae.2 Pathological effects of transgenic Bt rice expressing a gene of cry1Ab on the larval midgut of rice leaf-foldersThe pathological changes of the larval midgut of rice leaf-folders after feeding with Bt rice line KMD1 and KMD2 was studied using electron microscopy. Ultrastructural investigations of the anterior midgut showed cellular alternations in larvae, such as swelling of mitochondria, endoplasmic reticulum, and dilatation of intercellular spaces, fenestration or disorganization of the Golgi complex, and concentric arrangement of rough endoplasmic reticulum. The initial infected organelles were mitochondria. As the pathological process went on, the upper portions of the cells swelled, and cytoplasm in these regions decreased in electronic density and other organelles were damaged to a certain degree, such as wiredraw of nucleus, condensation of nuclear, and the increase of number of rough endoplasmic reticulum. As the infection proceed still further, pathological changes in the mitochondrial abundant areas of basal membrane enfoldings of columnar cells and cytoplasmic projections of goblet cells became more obvious. Finally the midgut epithelium cells disrupted and sloughed off from the basal membrane. 3 Sugar and protein content in the haemolymph of rice leaf-folder larvae after fed with the transgenic Bt riceProtein concentration in the haemolymph of rice leaf-folders (third- or fifth-instar) fed with KMD1 or KMD2 was lower than that of the control Xiushui 11, and the difference was not significant, while there was no significant difference among different times after treatment.Total sugar content in the haemolymph of rice leaf-folders fed with KMD1 or KMD2 was lower than that of the control, and the difference was not significant. Similarly, the trehalose content in the haemolymph of rice leaf-folders fed with KMD1 or KMD2 was lower than that of the control, and the difference was also not significant.4 Influence of Bt rice on the digestible proteinase activity in the midgut of rice leaf-folders after fed with transgenic Bt riceThe influence of Bt rice line KMD1 and KMD2 on the digestive enzymes of rice leaf-folders was tested. We measured the activities of some digestive enzymes in the larval midgut, including trypsin-like proteinase and chymotrypsin-like proteinase within different time after treatment. The activities of the total proteinase were higher than the controls, but not significantly. While the activities of the weak alkaline trypsin-like and the active alkaline trypsin-like enzymes generally trend to decline, the same as the chymotrypsin-like enzymes activies.5 Effects of the health and damaged (by rice leaf-folders) transgenic Bt rice on the behavioral responses of Apanteles cypris NixonThe behavioral responses of Apanteles cypris Nixon to the transgenic Bt rice (KMD1 and KMD1) and the control rice Xiushui 11 were studied with a Y-tube olfactometer. The results indicated that health Bt rice and non-Bt rice all had attraction to Apanteles cypris Nixon compared with clean air; Apanteles cypris Nixon has preference to the KMD1 rice on health plants; among the damged Bt rice and non-Bt rice plants, Apanteles cypris Nixon preferred the volatiles of non Bt rice.6 Impacts of transgenic rice lines on biological characteristics of Apanteles cypris NixonThe developments of Apanteles cypris Nixon were suppressed when A. cypris Nixon parasitized rice leaf-folder larvae fed with Bt rice. The results showed that the adult longevity of the male A. cypris Nixon, and female A. cypris Nixon parasitized in 2nd instar larvae of rice leaf-folder, cocooning rates and rates of eclosion, weights of adult wasp, weight of cocoon parasitized in third- instar larvae of rice leaf-folders, and the length of the front-wing were all lower than those parasitized in larvae fed with non-Bt rice Xiushui 11. No significant difference were observed on cocoon-larvae duration, the length of the cocoon, and the length of the front wings which parasitized in 2nd instar larvae RLF fed with Bt rice. 7 Biotransfer and bioaccumulation of Cry1Ab insecticidal protein in rice plant-rice leaf folder-Apanteles cypris Nixon food chainThe concentration of Cry1Ab insecticidal protein expressed in the two homozygous transgenic Bacillus thuringiensis (Bt) rice lines, KMD1 and KMD2, were determined by enzyme-linked immunosorbent assay (ELISA) with the Pathoscreen kit for Bt cry1Ab/Ac protein (Agdia, USA). The results showed that the concentration of Cry1Ab expressed both in KMD1 and KMD2 at heading and maturing stage were significantly lower than that at seedling, tillering and booting stage. The quantitative cycle of Cry1Ab insecticidal protein in the food chain of transgenic rice plants and its target pest leaf folder, Cnaphalocrocis medinalis (Guenee) as well as the parasitoid wasp Apanteles cypris Nixon was analyzed using the kit. After being fed on KMD1 or KMD2 rice plants for 12 hours, Cry1Ab protein could be detected in the bodies of rice leaf folders. However, as the feeding time increased, the content of Cry1Ab remaining in RLF body did not show the tendency of increase. Also, Cry1Ab protein could be detected in the bodies of parasitoid wasp parasitizing in the RLF reared on KMD1 or KMD2 rice plants for increasing time, while their contents were less than those of RLF fed on KMD1 or KMD2 for the same time. It is clear that Cry1Ab protein could be transferred from transgenic rice to its target pest, RLF, and then to its parasitoid, Apanteles cypris Nixon in the food chain, but no bioaccumulation pattern of Cry1Ab protein was observed. Additionally, contents of Cry1Ab protein in the excretion of RLF were observed, and also did not show the tendency of increase with the feeding time increased.8 Effects of the transgenic Bt rice on the arthropod abundance and diversity in the paddy fieldsIn a 3-yr field experiment, possible effects of transgenic Bt rice on the arthropod communities under paddy-field condition were assessed in terms of arthropod guild dominance, family composition, dominance distribution of each guild, individuals of each guild and some common community indices (including species richness, Shannon-Weaver diversity index, evenness index and dominant concentration index). Our results overall suggested no significant differences between the Bt and control rice plots in such arthropod community specific parameters. The similarity of arthropod community between the Bt and control rice plots was apparently high. It is clear that Bt rice generally shows no marked negative effects on the arthropod community in paddy fields.