| The Asian Longhorn Beetle (ALB), Anoplophora glabripennis (Motschulsky) (Coleoptera:Cerambycid ae:Lamiinae:Lamiini) is one of the most important forest pests and widely distribute in China, and caused great losses to the forest. Poplars (Populus spp.), willows (Salix spp.), maples (Acer spp.) and elm (Ulmus spp) are the primary host tree species.Because of the serious threat posed by A. glabripennis, a large amount of research of cellulase and host selection has focused on this species in recent years, but the relationship of cellulase and host selection is unclear.To investigate the relationship between cellulase activity and host selection, A. glabripennis larvae and adults from four different host tree species (Populus alba L. var. bolleana Bunge; P. nigra var. thevestina (Dode)Bean; P. simonii Carriere×P. alba var. pyramidlis cv. opera Hsu., and Salix matsudana f. lobato-glandulosa Fang & Liu), adults fed on five different tree species (Ailanthus altissima Swingle, P. tomentosa Carriere, P. simonii Carriere×P. alba var. pyramidlis cv. opera Hsu., S. matsudana Koidz, and Acer negundo L.), adults fed on original and non-original host tree species, insect in different state and larvae in different instars were selected.The enzyme activities of endoglucanase, exoglucanase and (3-glucosidase in the intestines of the insects were measured, the endoglucanase isozymes were detected with a CMC-incorporated polyacrylamide gel, and the intestinal tissue paraffin section of A. glabripennis were also been observed. The results show that:(1) Adults and larvae from four different host tree species (P. alba L. var. bolleana Bunge; P. nigra var. thevestina (Dode)Bean; P. simonii Carriere×P. alba var. pyramidlis cv. opera Hsu., and S. matsudana f. lobato-glandulosa Fang & Liu) were chosen, and three kinds of cellulase activities in the intestines of the insects were measured.The results were:there were no significant differences in the activities of endoglucanase, exoglucanase andβ-glucosidase in males and females emerging from different host tree species. When adults emerged from the same host tree species, there were no significant differences in the activities of exoglucanase andβ-glucosidase between males and females, but the activity of endoglucanase in males was clearly higher than that in females. There were no significant differences in endoglucanase, exoglucanase andβ-glucosidase activities between larvae from different host tree species.The endoglucanase isozymes were detected with a CMC-incorporated polyacrylamide gel, the patterns and migration of endoglucanase isozymes of males and females emerging from different host tree species are clearly not different, neither are they different when emerging from the same hosts. No difference in larvae from different host tree species.From the results, it can be concluded that there exists strong consistency between the enzyme activities of cellulase and isozymes patterns. There were no significant differences between the cellulase activities in A. glabripennis from different host tree species, as well as the endoglucanase isozymes patterns.This show that, there is no obvious relevance between cellulase and the larvae host tree species in A. glabripennis.(2) Adults were emerging from opera poplar, fed them with fresh branches of A. altissima Swingle, P. tomentosa Carriere, P. simonii Carriere×P. alba var. pyramidlis cv. opera Hsu., S. matsudana Koidz, and A. negundo L. respectively for three days.Cellulase activities were measured. The results were:Significant differences were found in the activities of endoglucanase between male and female fed on A. negundo L. and control, low activity of endoglucanase was occurred in both males and females fed on A. altissima Swingle. There were no significant differences in exoglucanase activities between males and females. Significant differences were noted inβ-glucosidase activity between male and female fed on A. negundo L., but there were no significant differences between male and female fed on other trees.As a kind of induced enzymes, this study found that, the kind of trees which the adults fed on has great effect on the activity of cellulase in adults, especially for endoglucanase. Thus, there is some relevance between cellulase and host tree selection in A. glabripennis adults.(3) Adults were emerging from P. simonii Carriere×P. alba var. pyramidlis cv. opera Hsu. and S. matsudana Koidz, fed them with fresh branches of P. simonii Carriere×P. alba var. pyramidlis cv. opera Hsu., S. matsudana Koidz and A. negundo L. respectively for three days.Cellulase activities were measured. The results were:In A. glabripennis adults from S. matsudana Koidz fed on different host tree species, there are no significant differences in the enzyme activities of endoglucanase between male and female fed on three host trees, neither inβ-glucosidase. No significant differences in the enzyme activities of endoglucanase andβ-glucosidase was found between male or female fed on three host tree species. In A. glabripennis adults from P. simonii Carriere×P. alba var. pyramidlis cv. opera Hsu. fed on different host tree species, there are no significant differences in the enzyme activities of endoglucanase between male and female fed on three host trees, neither in P-glucosidase. No significant differences in the enzyme activities of endoglucanase and P-glucosidase was found between male or female fed on three host tree species, except the endoglucanase activity in male fed on S. matsudana Koidz is lower than that fed on A. negundo L. and P. simonii Carriere×P. alba var. pyramidlis cv. opera Hsu..(4) In the research, extremely weak cellulase activity was detected in A. glabripennis pupae, not more than 0.06μmol (glucose)·g-1 (FW)·h-1, no significant differences in the enzyme activities of endoglucanase, exoglucanase and P-glucosidase between male pupae and female pupae. In the inner adults, no significant differences in the enzyme activities of endoglucanase, exoglucanase andβ-glucosidase between male and female.There was a great fluctuation in the cellulase activity, this may show that the cellulase system in A. glabripennis adults is gradually perfect after adult emergence till coming out of the emergence hole. (5) Larvae fed on host tree species under natural growth situation had a significant reduction in both endoglucanase andβ-glucosidase activities. The activities of endoglucanase in the first and second instars are significantly higher than the followed three instars, and the activities ofβ-glucosidase in the former three instars are significantly higher than the followed two instars. This trend also occurred in the larvae fed on artificial diet. The low cellulase activity of matured larvae may caused by low relative comsumption rate or stable cellulase activity level with increasing weight.(6) Intestine of A. glabripennis larvae, female and male were tookout, foregut, midgut and hindgut were distinguished and the cellulase activity was measured respectively, the results show that:90.4% endoglucanase activity and 93.4%β-glucosidase activity of larvae were distributed in midgut.65.4% endoglucanase activity and 94.2%β-glucosidase activity of female were distributed in midgut, and 31.5 %endoglucanase activity distributed in hindgut.89.0%endoglucanase activity and 92.0%β-glucosidase activity of male were distributed in midgut. Cystic structure was discovered in the intestinal tissue paraffin section of female A. glabripennis. This makes cellulase source in A. glabripennis, with a new assumption that cellulase in A. glabripennis larvae and male adult was secreted by itself, and A. glabripennis adult female digest natural cellulose with the participation of symbiotic microorganism in there hindgut. For verification of this speculation requires further study.
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