Cloning, ligand-binding, and temporal expression of ecdysteroid receptors in the diamondback moth, Plutella xylostella

BACKGROUND: The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a devastating pest of cruciferous crops worldwide, and has developed resistance to a wide range of insecticides, including diacylhydrazine-based ecdysone agonists, a highly selective group of molt-accelerating biopesticides targeting the ecdysone receptors. RESULT: In this study, we cloned and characterized the ecdysone receptors from P. xylostella, including the two isoforms of EcR and a USP. Sequence comparison and phylogenetic analysis showed striking conservations among insect ecdysone receptors, especially between P. xylostella and other lepidopterans. The binding affinity of ecdysteroids to in vitro-translated receptor proteins indicated that PxEcRB isoform bound specifically to ponasterone A, and the binding affinity was enhanced by co-incubation with PxUSP (Kd =3.0±1.7 nM). In contrast, PxEcRA did not bind to ponasterone A, even in the presence of PxUSP. The expression of PxEcRB were consistently higher than that of PxEcRA across each and every developmental stage, while the pattern of PxUSP expression is more or less ubiquitous. CONCLUSIONS: Target site insensitivity, in which the altered binding of insecticides (ecdysone agonists) to their targets (ecdysone receptors) leads to an adaptive response (resistance), is one of the underlying mechanisms of diacylhydrazine resistance. Given the distinct differences at expression level and the ligand-binding capacity, we hypothesis that PxEcRB is the ecdysone receptor that controls the remodeling events during metamorphosis. More importantly, PxEcRB is the potential target site which is modified in the ecdysone agonist-resistant P. xylostella

Dynamic Extra Buses Scheduling Strategy in Public Transport

This paper presents a dynamic extra buses scheduling strategy to improve the transit service of transit routes. In this strategy, in order to decide when to dispatch an extra bus, the service reliability of transit route is assessed firstly. A model aimed at maximizing the benefit of the extra buses scheduling strategy is constructed to determine how many stops extra buses need to skip from the terminal to accommodate passengers at the following stops. A heuristic algorithm is defined and implemented to estimate the service reliability of transit route and to optimize the initial stop of extra buses scheduling strategy. Finally, the strategy is tested on two examples: a simple and a real-life transit route in the Dalian city in China. The results show that the extra buses scheduling strategy based on terminal stops with a reasonable threshold can save 8.01% waiting time of passengers

Co-evolution of the mating position and male genitalia in insects: a case study of a hangingfly.

Hangingflies are unique for the male providing a nuptial gift to the female during mating and taking a face-to-face hanging copulation with the female. Their male genitalia are peculiar for an extremely elongated penisfilum, a pair of well-developed epandrial lobes (9th tergum), and a pair of degenerated gonostyli. However, the co-evolution of their face-to-face copulation behavior and the male genitalia has rarely been studied hitherto. In this paper the mating behavior of the hangingfly Bittacus planus Cheng, 1949 was observed under laboratory conditions, and the morphology of the male and female external genitalia was investigated using light and scanning electron microscopy. The male provides an insect prey as a nuptial gift to the female in courtship and mating process, and commits a face-to-face copulation. During copulation, the male abdomen twists temporarily about 180° to accommodate their face-to-face mating position. The aedeagal complex has an extremely elongated penisfilum, corresponding to the elongated spermathecal duct of the female. The well-developed epandrial lobes serve as claspers to grasp the female subgenital plate during copulation, replacing the function of gonostyli, which are greatly reduced in Bittacidae. The modified proctiger assists the penisfilum to stretch and to enter into the female spermathecal duct. The possible reasons why this species might mate face-to-face are briefly discussed

Light micrographs of a copulation pair of <i>B. planus</i>, lateral view.

<p>The white arrowhead shows the gonostylus of the male, the black arrowhead shows the female subgenital plate. Ce, cercus; EL, epandrial lobe; Gc, gonocoxite; Gs, gonostylus; S9, sternum IX; SgP, subgenital plate; Sp, spiracle; T6–8, terga VI to VIII. Scale bar  = 0.5 mm.</p

SEM micrographs of the male epandrial lobes, proctiger and cercus in <i>B. planus</i>.

<p>(A) Caudal view of the epandrial lobes and proctiger, showing the modified paired epandrial lobes and upper and lower branches of proctiger, the asterisks show stout spines which were regularly distributed along its inner posterior edge. (B) Magnification of the Inner view of the posterior margin of the epandrial lobes, showing the stout spines. (C) Magnification of cercus. A, anus; Ce, cercus; EL, epandrial lobe; LBP, lower branch of proctiger; UBP, upper branch of proctiger. Scale bars: (A)  = 200 μm; (B)  = 20 μm; (C)  = 50 μm.</p

SEM micrographs of the male genitalia in <i>B. planus</i>.

<p>(A) Caudo-ventral view. (B) Ventral view of the left gonostylus, showing the stylocavernula, a bundle of sensilla chaetica. (C) Dorsal view of the aedeagal complex, with the epiphallus and the support of ejaculatory sac removed, showing the sperm channel. (D) Lateral view of aedeagal complex. AL, aedeagal lobe; BAP, basal apodeme of phallobase; Eph, epiphallus; Gc, gonocoxite; Gs, gonostylus; LAA, lateral arm of apodeme of phallobase; LLP, lateral lumen of phallobase; Pb, phallobase; Pf, penisfilum; SC, sperm channel (median lumen of phallobase); SF, supporting frame of sperm channel; Stc, stylocavernula. Scale bars: (A), (C) and (D)  = 200 μm; (B)  = 50 μm.</p

The copulating phase of <i>B. planus</i>, showing the gradually insertion process of the male penisfilum (the left: female; the right: male).

<p>(A) The male firmly holds the subgenital plate of the female by his epandrial lobes and the elongated penisfilum is stretched by the upper and lower branches of the proctiger. (B) The proctiger assists the entering of the male penisfilum into the spermathecal duct of the female. (C) The partly inserted penisfilum. (D) The male penisfilum is fully inserted.</p

Female genitalia of <i>B. planus</i>.

<p>(A)–(C) Lateral, ventral, and caudal views of the female terminalia, arrowheads show the membranous structure in the apex of the subgenital plate. (D) Part of the female reproductive system, showing the elongate spermathecal duct. A, anus; Ce, cercus; CO, common oviduct; LAG, lateral accessory gland; LO, lateral oviduct; SaP, subanal plate; SgP, subgenital plate; Sp, spermatheca; SpD, spermathecal duct; T8–9, terga VIII and IX. Scale bars: (A) and (B)  = 0.5 mm; (C)  = 200 μm; (D)  = 0.2 mm.</p

Transit network design based on travel time reliability

This paper presents a transit network optimization method, in which travel time reliability on road is considered. A robust optimization model, taking into account the stochastic travel time, is formulated to satisfy the demand of passengers and provide reliable transit service. The optimization model aims to maximize the efficiency of passenger trips in the optimized transit network. Tabu search algorithm is defined and implemented to solve the problem. Then, transit network optimization method proposed in this paper is tested with two numerical examples: a simple route and a medium-size network. The results show the proposed method can effectively improve the reliability of a transit network and reduce the travel time of passengers in general

A bi-level programming for bus lane network design

This paper proposes a bi-level programming model to solve the design problem for bus lane distribution in multi-modal transport networks. The upper level model aims at minimizing the average travel time of travelers, as well as minimizing the difference of passengers’ comfort among all the bus lines by optimizing bus frequencies. The lower level model is a multi-modal transport network equilibrium model for the joint modal split/traffic assignment problem. The column generation algorithm, the branch-and-bound algorithm and the method of successive averages are comprehensively applied in this paper for the solution of the bi-level model. A simple numerical test and an empirical test based on Dalian economic zone are employed to validate the proposed model. The results show that the bi-level model performs well with regard to the objective of reducing travel time costs for all travelers and balancing transit service level among all bus lines