两种入侵福寿螺杂交-渐渗及对温度适应的分子机制研究

A significant increase in the occurrence of interspecific hybrids in wild environments has been observed in recent decades due to global changes caused by human activities such as the introduction of exotic species, habitat alterations, and contact with artificial hybrids from aquaculture. Hybridization-Invasion (H-I) hypothesis has received particular attention in the past following the publication of Ellstrand & Schierenbeck (2000). Hybridization can create novel phenotypes relative to the parental taxa, increasing the likelihood of survival and establishment success in novel habitats. Hybridization can also lead to increased phenotypic and genetic variation relative to the parental taxa, which may help hybrids better cope with environmental stochasticity and increase their evolutionary potential. If the parental taxa are relatively isolated and occur in small populations, hybridization could lead to the purging of genetic load, and the resulting fitness boost could increase invasiveness. H-I hypothesis is moderately supported across taxa, with strong support in some systems (particularly plants), while more tests in animal and fungal taxa need to be done. While the hybridization of non-native species with native species has been documented in a wide range of organisms, including plants, amphibians, fishes, mammals and insects, few cases of hybridization involving two invasive species in non-native areas have been described. However, multiple related species may also be introduced to the same new environment, and hybridization between two introduced taxa may not be less uncommon than imagined. .Apple snails provide a good model system to study the hybridization involving two invasive species in non-native areas. Previous studies suggested that Pomacea canaliculata and P. maculata have invaded in China, but the distributions of P. canaliculata and P. maculata are different. P. canaliculata is widely distributed in most southern China, while P. maculata is currently found only in several regions. Phylogenetic analysis based on sequences of the nuclear gene elongation factor 1-alpha (EF1a) and microsatellites detected genetic exchange between P. canaliculata and P. maculata especially in the sympatric area of the two species. Temperature limits the range of many apple snails as it is a key determinant of their activity thresholds, growth, reproduction, development and survival. Although numerous studies have examined physiological changes on temperature response in P. canaliculata and P. maculata, few have investigated genetically based species differences in thermal tolerance. Using transcriptomics, gene expression changes can be quantified and related to evolutionary and ecological processes. Here we will use hybrid experiments and microsatellite to assess cross-species hybridization and genetic introgression between invasive P. canaliculata and P. maculata. We will compare the transcriptomic data of the gill and liver tissues from females in P. canaliculata, P. maculata and their F1 hybrids, and temperature tolerance in F1 hybrids and backcross. This research aims to clarify the role of hybridization between the two invasive apple snails in their range expansion in invaded area and identify genes that are differentially expressed following temperature stress to obtain a better understanding of how temperature can regulate gene expression and affect thermotolerance and cold tolerance in these two invasive apple snails.

杂交-入侵假说认为杂交能够增加表型变异和遗传变异，降低群体遗传负荷，有利于杂交个体适应变化的环境，增强它们的进化潜力以及入侵性。越来越多的研究证实杂交在植物入侵过程中发挥了重要的作用。但对动物入侵是否具有相似的作用还缺乏足够的证据。福寿螺为研究近缘动物在入侵地的杂交提供了很好的材料。我们前期的研究工作表明入侵中国的福寿螺包括Pomacea canaliculata和 P. maculata。P. canaliculata在我国广泛分布，而P. maculata分布范围较局限，它们在同域分布地区存在杂交的可能。温度是限制福寿螺分布的关键因素之一。本项目拟通过杂交实验和微卫星标记探讨我国两种福寿螺杂交-渐渗的程度和方向，基于转录组水平比较两种福寿螺及杂交子代对不同温度适应能力的差异，阐明杂交-渐渗在福寿螺入侵中的作用，揭示福寿螺适应环境温度的分子调控机制，为福寿螺的防治和管理提供科学依据。

杂交-入侵假说认为杂交能够增加表型变异和遗传变异，有利于杂交个体适应变化的环境，增强它们的进化潜力以及入侵性。本项目基于全基因组重测序技术分析了入侵中国7个省市的108只福寿螺。研究结果表明,小管福寿螺和斑点福寿螺、小管福寿螺和新种P. occulta nov. sp.在同域分布地区存在广泛杂交，并且可能在引入前或引入过程中3种福寿螺之间就已经发生了渐渗杂交。温度是限制福寿螺分布的关键因素之一，小管福寿螺在中国长江以南大部分地区广泛分布，但斑点福寿螺分布较为局限。本项目基于转录组研究发现，小管福寿螺和斑点福寿螺在应对高温和低温的胁迫中表现出不同的基因表达模式。在高温胁迫下，小管福寿螺免疫相关基因表达量下降，斑点福寿螺主要通过降解受损或折叠错误的蛋白质来减少高温对机体造成的的损伤。热休克蛋白基因和细胞色素P450基因在两种福寿螺应对低温胁迫中发挥重要作用。冷驯化处理会诱导小管福寿螺大量基因表达以减少低温胁迫造成的损伤, 通过代谢调整，激活泛素-蛋白酶体系统降解受损或折叠错误的蛋白质，减少氧化应激损伤和提高不饱和脂肪酸胆固醇含量提高小管福寿螺耐寒性。lncRNA可以通过调控E3泛素蛋白连接酶、谷胱甘肽巯基转移酶合成、葡萄糖转运和细胞色素P450等基因的表达参与冷驯化提高小管福寿螺耐寒性。在小管福寿螺基因组中鉴定出33个DnaJ基因和30个GST基因。经冷驯化处理后，5个DnaJ基因在小管福寿螺肝胰腺中的表达量显著提高。10个GST基因为耐寒性差异表达基因，有5个GST基因参与冷驯化过程。上述研究探讨了两种福寿螺适应环境温度的分子调控机制，有助于了解不同福寿螺对环境温度适应能力的差异及其与分布现状的关系，为入侵福寿螺的防治和管理提供科学参考。

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