海洋哺乳動物因其適應(yīng)與陸地截然不同的海洋環(huán)境,，具有重要的進化意義。但到目前為止,，關(guān)于它們在海洋環(huán)境中生存的遺傳基礎(chǔ)方面的研究非常有限,。
長須鯨
中國科學(xué)院昆明動物研究所張亞平院士、云南大學(xué)于黎研究員和博士研究生靳偉通過對海洋哺乳動物和陸地哺乳動物的犁鼻器系統(tǒng)特異表達基因——瞬時受體電位基因（TRPC2）的研究,，為哺乳動物從陸地到海洋轉(zhuǎn)變過程中的信息素感知方面的進化提供了重要信息,。信息素在哺乳動物生殖和社會行為方面起重要作用，主要由犁鼻器系統(tǒng)感知,。
該研究顯示,，完全適應(yīng)于海洋生活的鯨目（長須鯨）的TRPC2基因是假基因，選擇壓力明顯放松,，基因功能喪失,，而營半水生生活的加利福尼亞海獅的TRPC2基因是功能基因，仍然受到較強的選擇壓力。因此推測,，鯨類因其完全適應(yīng)于海洋生活,，退化的犁鼻器信息素感知功能促使TRPC2基因假基因化，而對于“兩棲”的加利福尼亞海獅來說,，陸地生活仍然需要犁鼻器信息素感知,，因此其TRPC2基因仍然是功能基因。進一步分析表明,，犁鼻器信息素信號傳導(dǎo)通路可能在鯨目的共同祖先時（32-53百萬年之間）就已失去功能。令人驚奇的是,，與加利福尼亞海獅不同,，同樣營半水生生活的港海豹和歐亞水獺的TRPC2基因都是假基因。TRPC2基因很有可能在港海豹和歐亞水獺中獨立假基因化和喪失功能（分別大約在2.7百萬年和1.8百萬年后）,。其它未知的選擇壓力或感覺器官補償機制可能促使了港海豹和歐亞水獺的TRPC2基因假基因化,。（生物谷Bioon.com）
生物谷推薦原始出處：
Molecular Biology and Evolution, doi:10.1093/molbev/msq027
Characterization of TRPC2, an essential genetic component of VNS chemoreception provides insights into the evolution of pheromonal olfaction in secondary-adapted marine mammals
Li Yu*,$, Wei Jin*,,$, Jia-xin Wang*, Xin Zhang*, Meng-meng Chen, Zhou-hai Zhu*, Hang Lee&, Muyeong Lee& and Ya-ping Zhang*,
* Laboratory for Conservation and Utilization of Bio-resource & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, 650091, PR, China
State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
The school of life science, Yunnan University, Kunming, 650200, China
& Conservation Genome Resource Bank for Korean Wildlife, Research Institute for Veterinary Science and Coll. of Vet. Med., Seoul National Univ., Seoul 151-742, South Korea
Pheromones are chemical cues released and sensed by individuals of the same species, which are of major importance in regulating reproductive and social behaviors of mammals. Generally, they are detected by the vomeronasal system (VNS). Here, we first investigated and compared an essential genetic component of vomeronasal chemoreception, i.e., TRPC2 gene, of four marine mammals varying the degree of aquatic specialization and related terrestrial species in order to provide insights into the evolution of pheromonal olfaction in the mammalian transition from land to water. Our results based on sequence characterizations and evolutionary analyses, for the first time, show the evidence for the ancestral impairment of vomeronasal pheromone signal transduction pathway in fully-aquatic cetaceans, supporting a reduced or absent dependence on olfaction as a result of the complete adaptation to the marine habitat, while the amphibious California sea lion was found to have a putatively functional TRPC2 gene, which is still under strong selective pressures, reflecting the reliance of terrestrial environment on chemical recognition among the semi-adapted marine mammals. Interestingly, our study found that, unlike that of the California sea lion, TRPC2 genes of the harbor seal and the river otter, both of which are also semi-aquatic, are pseudogenes. Our data suggests that other unknown selective pressures or sensory modalities might have promoted the independent absence of a functional VNS in these two species. In this respect, the evolution of pheromonal olfaction in marine mammals appears to be more complex and confusing than has been previously thought. Our study makes a useful contribution to the current understanding of the evolution of pheromone perception of mammals in response to selective pressures from an aquatic environment.
