As a key enzyme of catecholamine synthesis, tyrosine hydroxylase is an indispensable enzyme of metabolism in insects, mammals and human. Tyrosine hydroxylase involves in the synthesis of melanin, affects the body color and insect exoskeleton hardening. In order to explore the physiological and biochemical function of tyrosine hydroxylase, in this study, the structure, expression profile and function of tyrosine hydroxylase gene were studied in the silkworm, Bombyx mori, using the combined methods of bioinformatic analysis and experiments. The bioinformatic analysis based on the silkworm genome database and microarray database indicated that the silkworm tyrosine hydroxylase gene BmTh is located on chromosome 1. BmTh includes 8 exons and encodes a protein with 561 amino acid residues. Microarray data in different tissues showed that it has significant expression signals in head and epidermis of day-3 5th instar larvae, which was verified by RT-PCR. In situ hybridization analysis showed that there was remarkable signal on the rim of head and epidermis with paraffin tissue section and RNA probe. Through injecting an inhibitor of tyrosine hydroxylase (3-indole-L-tyrosine, 3-IT) at different concentrations into silkworm larva at the mounting stage, we found that 20 mmol/L 3-IT had no influence on the larval development, 50 mmol/L 3-IT could handicap the larval metamorphosis and pupation, and 100 mmol/L 3-IT could cause the larval death and turn the larval body color into black. These results suggest that tyrosine hydroxylase plays an important role in the processes of metamorphosis and it is an indispensable key enzyme for normal development in the silkworm.

【Aim】 Pyridoxal kinase (PLK, EC 2.7.1.35) is a key enzyme related to vitamin B6 metabolism. In this study, recombinant pyridoxal kinase of Bombyx mori will be expressed, which will lay a foundation for further study on regulation mechanism, catalytic mechanism and structure of PLK in B. mori.【Methods】 After fusion expression vector harboring PLK gene of B. mori was constructed, the recombinant vector was transformed to Escherichia coli Rosetta for induction and expression, and then the characteristics of the purified recombinant protein was analyzed after the expression product was purified using affinity chromatography by Ni²⁺ column. 【Results】 Only one band was observed when the purified PLK was separated on SDS-PAGE. The PLK was enriched by 40fold and its specific activity was 1 800 U/mg. The optimum temperature and pH of this enzyme was about 50℃, and 5.5-6, respectively, and Zn²⁺ was the effective activator in enzymatic reaction. 【Conclusion】 The recombinant PLK exhibited the same catalytic characteristics as the native protein obtained from tissues of B. mori.

 In order to explore the effects of heavy metals on insect cellular immunity and its related mechanism, the differences in the number, viability, spreading and encapsulation rates, and morphology of hemocytes between the Cd²⁺ treated (at the concentration of 150 μg/g) Boettcherisca peregrina and its control were investigated and compared, respectively, using the methods as hemocytes counting, typan blue staining, spreading and encapsulation assays, as well as microstructure and ultrastructure observations. The results indicated that at 24, 48, 72 and 96 h post feeding the neonate larvae of B. peregrina with the artificial diet containing Cd²⁺, both total hemocyte count and hemocytes viability in the larvae were significantly decreased compared with the control, respectively. In contrast, the in vitro spreading rate and encapsulation capability of hemocytes of the larvae exposed to Cd²⁺ were significantly lower than those of the control after 72 and 48 h exposure, respectively, and then showed no significant differences with the control. Additionally, the in vivo encapsulation capability of hemocytes of the pupae that developed from the larvae exposed to Cd²⁺ was also significantly lower than that of the control. The morphological observation results showed that compared with the control, no marked alternation in the microstructure was observed for each type of hemocytes (including prohemocyte, plasmatocyte, granulocyte and oenocytoid), except that some plasmatocytes neither spread nor extended their pseudopods. However, the ultrastructure of each type of hemocytes in the exposed larvae was found to be alternated to various degrees compared to the control, with the main ultrastructural alternation including: damage or break of cell membrane, condensation of chromatin, sharply decreasing of the number of mitochondria, endoplasmic reticulum and other organelles, and the emergence of vacuoles in cytoplasm. The results suggest that heavy metal Cd²⁺ may have toxic effects on hemocytes of B. peregrina.

 WO phage is the bacterial virus infecting Wolbachia in arthropods. It is supposed that WO phage may participate in controlling genetic changes of the hosts. Laodelphax striatellus planthoppers from four geographic populations of China (Minhang, Shanghai; Puer, Yunnan; Jining, Shandong; Qingtongxia, Ningxia) were bred on rice treated with antibiotics. The infection rates of Wolbachia and WO phage were examined every twenty days, and the infection relationships between Wolbachia and WO phage were analyzed based on the data obtained. The results revealed that the infection rate of Wolbachia declined with time, and so was WO phage. By using Real-time quantitative PCR, we found that the copy numbers of Wolbachia and WO phage varied with the developmental stages of adult female, displaying the highest quantity at 8 d post infection, and WO phage density showed the same pattern as that of Wolbachia. From the results, we inferred that WO phage is the obligate virus infecting Wolbachia, and the WO phage infecting Wolbachia in L. striatellus may be lysogenic.

When attacked by herbivores, plants produce defense responses, and the jasmonic acid (JA) signaling pathway plays an important role in this process. So far, however, little was known about the herbivore-induced defense responses in Chinese cabbage (Brassica campestris L.). Therefore, the defense responses of B. campestris attacked by Spodoptera litura (Fabricius) and their relations to the JA signaling pathway were studied through assaying the contents of JA and trypsin protease inhibitors (TrypPIs) in B. campestris plants. The results showed that infestation by S. litura resulted in systemic increases in levels of both JA and TrypPIs in B. campestris plants, of which the level of TrypPIs could also be systemically induced by exogenous application of methyl jasmonate (MeJA). Moreover, body weights of S. litura caterpillars fed on leaves treated by MeJA or infested by the herbivore decreased significantly, only 67.5% and 60.2% of that fed on control leaves, respectively. Treatment with wounding plus the caterpillar oral spit (OS) could cause the increase in JA and TrypPIs level in the treated leaves, but its induction efficacy was similar to that induced by wounding plus water (W) and far lower than that induced by the herbivore infestation. The levels of JA and TrypPIs in OS- or W-treated plants were 68.4% and 62.9%, and 22.4% and 36.9% of those in control plants, respectively. We also found that there was no significant difference in the induction efficacy between the treatments “wounding once” and “wounding multiple times”. The results suggest that the defense responses of B. campestris plants induced by the herbivore are related to the JA signaling pathway, and elicitation of the responses is probably involved in the specific feeding behavior of the herbivore.

 Wolbachia is a common and widespread group of symbiotic bacteria found in arthropods, which is transmitted through the egg cytoplasm and can manipulate reproduction in their hosts in various ways. So, it has important potential significance on the research of evolution of arthropods and may be used in pest bio-control. Taking the Asian citrus psyllid (Diaphorina citri), the vector of the Huanglongbing(HLB) pathogen, as the research object, we detected the natural populations of Diaphorina citri from five areas, i.e., Beihai and Liuzhou in Guangxi, Shenzhen and Yangchun in Guangdong, and Fuzhou in Fujian, based on PCR amplification, cloning and sequencing of 16S rRNA, ftsZ and wsp genes. The obtained sequences were aligned with the published ones in database of NCBI, and the phylogenetic relationships among Wolbachia types found in D. citri and other insect species were analyzed. The results indicated that all the five populations of D. citri were infected by Wolbachia. The three gene sequences of Wolbachia and the phylogenetic tree analysis showed that Wolbachia population in D. citri belongs to supergroup B.  Further phylogenetic analysis based on the wsp gene sequences showed that the Wolbachia of D. citri belongs to Con subgroup. The 16S rRNA, ftsZ and wsp gene sequences were almost identical in the five geographic populations, respectively, and the identity is up to 99%, showing that these three gene sequences of Wolbachia in different geographic populations of D. citri had no significant difference. The results can provide useful information for understanding evolution of citrus psyllids and their integrated control.