Antimicrobial peptide cecropin B functions in pathogen resistance of Mythimna separata.

Mythimna separata (Lepidoptera: Noctuidae) is an omnivorous pest that poses a great threat to food security. Insect antimicrobial peptides (AMPs) are small peptides that are important effector molecules of innate immunity. Here, we investigated the role of the AMP cecropin B in the growth, development, and immunity of M. separata. The gene encoding M. separata cecropin B (MscecropinB) was cloned. The expression of MscecropinB was determined in different developmental stages and tissues of M. separata. It was highest in the prepupal stage, followed by the pupal stage. Among larval stages, the highest expression was observed in the fourth instar. Tissue expression analysis of fourth instar larvae showed that MscecropinB was highly expressed in the fat body and haemolymph. An increase in population density led to upregulation of MscecropinB expression. MscecropinB expression was also upregulated by the infection of third and fourth instar M. separata with Beauveria bassiana or Bacillus thuringiensis (Bt). RNA interference (RNAi) targeting MscecropinB inhibited the emergence rate and fecundity of M. separata, and resulted in an increased sensitivity to B. bassiana and Bt. The mortality of M. separata larvae was significantly higher in pathogen plus RNAi-treated M. separata than in controls treated with pathogens only. Our findings indicate that MscecropinB functions in the eclosion and fecundity of M. separata and plays an important role in resistance to infection by B. bassiana and Bt.

Expression patterns and antifungal function study of KaSPI in Mythimna separata.

Kazal-type serine protease inhibitors (KaSPI) play important roles in insect growth, development, digestion, metabolism and immune defence. In this study, based on the transcriptome of Mythimna separata, the cDNA sequence of MsKaSPI with Kazal domain was uploaded to GenBank (MN931651). Spatial and temporal expression analysis showed that MsKaSPI was expressed at different developmental stages and different tissues, and it was induced by 20-hydroxyecdysone in third-instar larvae of M. separata. After 24 h infection by Beauveria bassiana, the expression level of MsKaSPI and the corresponding MsKaSPI content were significantly up-regulated, being 6.42-fold and 1.91-fold to the control group, respectively, while the activities of serine protease, trypsin and chymotrypsin were inhibited. After RNA interference interfered with MsKaSPI for 6 h, the expression decreased by 73.44%, the corresponding content of MsKaSPI protein decreased by 55.66% after 12 h, and the activities of serine protease and trypsin were significantly enhanced. Meanwhile, both the larval and pupal stages of M. separata were prolonged, the weights were reduced and the number of eggs per female decreased by 181. Beauveria bassiana infection also increased the mortality of MsKaSPI-silenced M. separata by 18.96%. These prove MsKaSPI can not only result in slow growth and low fecundity of M. separata by regulating the activity of related protease, but also participate in the resistance to pathogenic fungi by regulating the serine protease inhibitor content and the activities of related serine protease.

Trehalose-6-phosphate synthase regulates chitin synthesis in Mythimna separata.

Trehalose is a substrate for the chitin synthesis pathway in insects. Thus, it directly affects chitin synthesis and metabolism. Trehalose-6-phosphate synthase (TPS) is a crucial enzyme in the trehalose synthesis pathway in insects, but its functions in Mythimna separata remain unclear. In this study, a TPS-encoding sequence in M. separata (MsTPS) was cloned and characterized. Its expression patterns at different developmental stages and in diverse tissues were investigated. The results indicated that MsTPS was expressed at all analyzed developmental stages, with peak expression levels in the pupal stage. Moreover, MsTPS was expressed in the foregut, midgut, hindgut, fat body, salivary gland, Malpighian tubules, and integument, with the highest expression levels in the fat body. The inhibition of MsTPS expression via RNA interference (RNAi) resulted in significant decreases in the trehalose content and TPS activity. It also resulted in significant changes in Chitin synthase (MsCHSA and MsCHSB) expression, and significantly decrease the chitin content in the midgut and integument of M. separata. Additionally, the silencing of MsTPS was associated with a significant decrease in M. separata weight, larval feed intake, and ability to utilize food. It also induced abnormal phenotypic changes and increased the M. separata mortality and malformation rates. Hence, MsTPS is important for M. separata chitin synthesis. The results of this study also suggest RNAi technology may be useful for enhancing the methods used to control M. separata infestations.

[The Relationship Between Oral Microbiota and Chronic Obstructive Pulmonary Disease].

Oral microbiota have a complex impact on the host's health and disease states. It has been found that the composition of lung flora bears a striking resemblance to the composition of oral flora. Moreover, oral pathogenic bacteria have been detected in the sputum and bronchoalveolar lavage fluid of patients with chronic obstructive pulmonary disease (COPD), suggesting that oral microbiota play an important role in the pathogenesis and development of COPD. Findings from lots of studies have shown that oral microbiota may participate in the pathogenesis and development of COPD through non-specific immune response, specific immune response, and the activities of protein hydrolase. Herein, we mainly summarized the available evidence on the relationship between oral microbiota and COPD. By examining the relationship between the two, we elaborated on the application of oral microbiota in the diagnosis and prevention of COPD, discussed possible directions for future research, and provided references for developing new therapeutic approaches.

Effects of melatonin on testicular function in adult male mice under different photoperiods.

Photoperiod is an important environmental factor affecting animal physiological function. Melatonin is an endogenous hormone that plays an important role in circadian and seasonal (or cyclical) rhythms and seasonal reproduction in mammals. To investigate the effects of melatonin on the reproductive performance of adult male mice under different photoperiods, sixty mice were randomly allotted to six groups: control (Light Dark, 12 L:12 D), control plus melatonin (MLD, 12 L:12 D), 24-hour continuous light (LL, 24 L:0 D), 24-hour continuous light plus melatonin (MLL 24 L:0 D), constant darkness (DD, 0 L:24 D), and constant darkness plus melatonin (MDD, 0 L:24 D). Normal saline (100 µL) was injected into the LD, LL, and DD groups at noon each day; the MLD, MLL, and MDD groups were injected with melatonin (1 mg/mL; 2 mg/kg·body weigh). After 24 hours of prolonged light exposure, testis morphology decreased, convoluted seminiferous tubules became sparse, the diameter of convoluted seminiferous tubules decreased, and the level of sex hormones decreased. After the administration of exogenous melatonin, testicular morphology and sex hormone levels decreased in the MLD group under normal light conditions. In the MLL group, the testicular tissue morphology returned to normal, the diameter of convoluted tubules increased, the hormone levels of LH (Luteinizing hormone) and MTL (melatonin) significantly increased (P<0.05), and th0e gene expressions of LHß and Mtnr1A (Melatonin receptors 1A) increased. There was almost no difference in the MDD group under continuous darkness. In conclusion, melatonin can damage the reproductive performance of male mice under normal light conditions, while exogenous melatonin can alleviate and protect the testicular injury of male mice under continuous light conditions.