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Phytoseiid mites frequently experience stress under changing or fluctuating environments especially in hot and dry agroecosystems. The mitogen-activated protein kinase (MAPK) signaling pathway is known to mediate environmental stress response involved in different signaling transduction pathways. In this study, a high temperature acclimated strain (HTAS) of Neoseiulus barkeri Hughes was developed from a conventional strain (CS) based on our previous study, and the functional differences of two MAPK genes, NbJNK and Nbp38, involved in defense responses were determined between the two strains. At 42 °C, the relative gene expression levels of the two MAPK genes increased rapidly in both N. barkeri strains. The expressions, however, decreased with an increase in duration of thermal treatment in the CS, while they remained elevated after 4 h of heat treatment in the HTAS. Silencing of two NbHSP70 genes by RNA interference (RNAi) significantly suppressed the expression levels of NbJNK and Nbp38, indicating a positive correlation between the protective response of HSP70 proteins and activation of the MAPK pathway. Heterologous overexpression of exogenous proteins encoded by NbJNK and Nbp38 significantly enhanced the viability of Escherichia coli Escherich BL21 under lethal temperature conditions. These results suggested that the thermotolerance of HTAS may be related to the sustained accumulation of MAPK genes. Elucidation of the functions of the MAPK signaling pathway in phytoseiids provides a novel perspective to the development of sustainable control strategies for small sap-feeding pests under thermal stress environments. [ABSTRACT FROM AUTHOR]

Cannibalism and intraguild predation (IGP) are two common interactions occurs in animal kingdom which influence their population structure and dynamics. Neoseiulus barkeri (Hughes) and Scolothrips takahashii (Priesner) are important natural enemies of citrus red mite Panonychus citri (McGregor). However, little was known about their interactions and how the availability of extraguild (EG) prey P. citri modulated their interactions. In this study, we determined incidences of cannibalism and intraguild predation of these two predators when different densities of extraguild prey P. citri were available. Our results showed that incidences of both cannibalism and IGP and were significantly reduced in the presence of the extraguild prey. The intraguild predation between N. barkeri and S. takahashii was bidirectional, but N. barkeri was a predominant intraguild predator over S. takahashii. The S. takahashii fed on immobile N. barkeri egg, and N. barkeri fed on inactive prepupa and pupa of S. takahashii, but the conspecifics seldom did. Our results indicated that the interactions of predators decreased significantly when prey was available. The predatory mite N. barkeri was a stronger interspecific competitor. The results of this study may be useful in developing effective biological control strategies against P. citri. [ABSTRACT FROM AUTHOR]

In our previous study, we reported a high temperature adapted strain (HTAS) of the predatory mite Neoseiulus barkeri was artificially selected via a long-term heat acclimation (35°C) and frequent heat hardenings. To understand the molecular basis of heat acclimation, 'omics' analyses were performed to compare the differences between HTAS female adults to conventional strain (CS) at transcriptional and translational levels. We obtained a total of 5,374 differentially expressed genes and 500 differentially expressed proteins. Among them, 119 transcripts had concurrent transcription and translation profiles. It's conserved that some processes, such as high expression of heat shock protein (HSP) genes, involved in heat tolerance of transcriptome analyses, while many protective enzymes including glutathione S-transferase, superoxide dismutase, peroxidase, and cytochrome P450 displayed down-regulated expression. KEGG analysis mapped 4,979 and 348 differentially expressed genes and proteins, to 299 and 253 pathways, respectively. The mitogen-activated protein kinases (MAPK) signaling pathway may provide new insights for the investigation of the molecular mechanisms of heat tolerance. Correlation enriched pathways indicated that there were four pathways associated with heat acclimation involving in energy metabolism and immunity. In addition, the expression patterns of ten randomly selected genes including HSP were consistent with the transcriptome results obtained through quantitative real-time PCR. Comparisons between transcriptome and proteome results indicated the upregulation of HSPs and genes participated in ATP production, immunity and energy metabolism process. A majority of antioxidant-related genes and detoxication-related genes were down-regulated suggesting a fitness cost of heat acclimation. Our results demonstrated that heat tolerance during a long-time acclimation of N. barkeri is a fairly complicated process of physiological regulations. These findings also contribute to a better understanding of the mechanisms of thermal responses of phytoseiid mites which could provide useful information for biological control through natural enemies. [ABSTRACT FROM AUTHOR]

In this paper, novel electrical machines having a separate permanent magnet (PM) excitation stator are proposed based on a partitioned stator (PS) flux reversal (FR) PM (FRPM) machine. Different from the conventional FRPM machines with a single stator, the PS-FRPM machines have two stators with PMs surface mounted in one stator and the armature windings located in another stator. This paper investigates the electromagnetic performance of PS-FRPM machines with 12/10, 12/11, 12/13, and 12/14 stator/rotor-pole, together with the influence of leading design parameters. The torque characteristics of PS-FRPM machines are quantitatively compared with the conventional FRPM machines based on their globally optimized designs. It shows that the PS-FRPM machines can generally produce higher torque when the PMs are thicker and exhibit >56% higher torque density than that of the conventional FRPM machines. Even compared under the same PM volume, the proposed PS-FRPM machines can have larger torque due to better utilization of the inner space. The investigation is validated by both finite-element and experimental results. [ABSTRACT FROM AUTHOR]