The Mating Strategy Of Bursaphelenchus Xvlophilus And Transcriptome Sequencing Of Mating Preference

With the acceleration of globalization and human disturbance in the ecological integrity ofthe system destruction, a large number of existing invasive species diffusion and outbreak ofserious risk of biological invasion has caused great disaster losses to the ecological system andhomeland security. Pine wood nematode (Bursaphelenchus xylophilus), as an agent of pine wiltdisease and the important quarantine target of many countries around the world, has beencaused many countries including china extremely serious economic, ecological and social loss.After infected a new tree, the PWN is propagated quickly in a short time within the stem ofpine trees and eventually death. The exploring of reproduction biology and ecologycharacterristics had important meaning for studing the high fecundity, ecology adaptationmechanism and providing a novel method to control pine wilt disease in future. It also couldprovide the theoretical basis of pathogesis and invasion mechanism.The study of mating choicebehavior of pine wood nematode, ecological mechanism and transcriptome sequencing ofmating preference were carried out. The main results are as follows.The mating behavior features of B. xylophilus by long-time microscope video andrepeated observation in one male and one female system. The mating behavior of B. xylophiluscould be decomposed into a series of sub-behaviors, including cruising, approaching,encountering, touching, hooping, locating, fixing, ejaculating, unfixing, quiescence androaming in sequence. According to the process of mating behavior, it could be divided into4different stages, i.e. searching, contacting, copulating and lingering stage. Time for differentstage varied significantly with21.8±2.0min,28.0±1.9min,23.6±0.7min and7.2±0.5min forfour mentioned stages respectively on average. Attraction between different sexes wasobviously observed, indicating that sexual pheromone might be involved in mating behavior ofB. xylophilus. In addition, mating choice of female to male was clearly observed. When onefemale was mixed with three males, male-male competition was obvious, which might be caused by the mating-choice pressure from female. Furthermore, intra-sexual competition offemale was also observed, but not obviously.Study on the choice characteristic of pine wood nematode in one male and one femalesystem (1♀+1♂), multiple females and one male system (3♀+1♂), one female and multiplemales system (1♀+3♂), multiple females and multiple males system (3♀+3♂). There weresignificantly differences in the whole mating process, the duration of different stages, durationof mating choice, contacting times and mating success rate for the first contact. The results ofmating efficiency of four systems showed that the mating efficiency in multiple females andone male system was189.6±2.1, significantly higher than that of one female and multiplemales system (110±0.8). Meanwhile, the sex ratio of offspring and ratio of adult to offspring inmultiple female and one male system were all higher than those of other systems. The offspringhad higher mating efficiency and may be more conducive to the breeding of the population.According to simulating the mating efficiency curves, the mating efficiency of pine woodnematode is the highest when the sexual ratio (female and male) is3.4:1, and the matingefficiency of female biased is higher than that of male biased. Mating strategy of pine woodnematode is accordance with status-dependent selection theory (SDS). In female biased system,Y mating strategy is used, the mating efficiency is high, sex ratio of offspring and ratio of adultto offspring is relatively high, the population is conducive to propagate quickly. In male biasedsystem, X mating strategy is used, the mating efficiency is low, sex ratio of offspring and ratioof adult to offspring is relatively low, the population is not conducive to propagate quickly.The results also showed that males adapted the intensity of competition according to thefemale’s selection intensity.Mating selection bias experiment and mating efficiency of virgin female, virgin male,mated female and mated male were determined. The results showed virgin female and matedfemale would preferred to mate with virgin male, but the mate preference of virgin male andmated male were not obvious. The results of mating efficiency determination showed themating efficiency of virgin or mated female when mated with virgin male were obviouslyhigher than that of mated with mated male and they increased24.8%and41.5%separately when the virgin female and mated female mated with virgin male. Meanwhile, the sex ratio ofoffspring and ratio of adult to offspring were significantly higher than those of mating withmated male. The mating efficiency of offspring was higher and more conducive to the breedingof population.Transcriptome sequencing was conducted when one virgin female encountered apotentialmate. The results showed that849genes were expressed individually when virgin female facedpotential mate,575genes were differentially expressed compared with virgin female existedalone. These functions of differentially expressed gene mainly included movement, stimulationresponse, reproduction, growth, development, death, metabolism, positioning, regulationl oftranscriptionand translation, antioxidant and organelles. Besides,69genes related to mating inother worms were selected.26genes were screened by gene function GO annotation whichrelated to stimulus response, breeding, positioning, and sports. The female mating choicemechanism will be elucidated by studying the influence of these genes and pathways on themating selection at the molecular level.