Historical biogeography and evolutionary diversification of Lilium(Liliaceae): New insights from plastome phylogenomics

Here, we infer the historical biogeography and evolutionary diversification of the genus Lilium. For this purpose, we used the complete plastomes of 64 currently accepted species in the genus Lilium(14plastomes were newly sequenced) to recover the phylogenetic backbone of the genus and a timecalibrated phylogenetic framework to estimate biogeographical history scenarios and evolutionary diversification rates of Lilium. Our results suggest that ancient climatic changes and geological tectonic activities jointly shaped the distribution range and drove evolutionary radiation of Lilium, including the Middle Miocene Climate Optimum(MMCO), the late Miocene global cooling, as well as the successive uplift of the Qinghai-Tibet Plateau(QTP) and the strengthening of the monsoon climate in East Asia during the late Miocene and the Pliocene. This case study suggests that the unique geological and climatic events in the Neogene of East Asia, in particular the uplift of QTP and the enhancement of monsoonal climate, may have played an essential role in formation of uneven distribution of plant diversity in the Northern Hemisphere.

虚拟筛选技术在黑色素生成抑制剂研发中的应用

黑色素含量水平及其分布被认为是影响肤色的重要因素。在黑色素生成过程中,酪氨酸酶(TYR)是调节黑色素含量的关键限速酶。小眼畸形相关转录因子(MITF)是黑色素细胞的主要调控因子,在黑色素细胞的分化和增殖中发挥着关键作用。大量研究表明通过降低TYR活性或稳定性,或干扰MITF正常转录,可预防或缓解黑色素生成异常而产生的各种皮肤问题。虚拟筛选具有成本低、效率高的优点,该技术应用于筛选黑色素生成抑制剂的研究具有良好的应用前景。本文总结了黑色素的合成和调控规律,综述了虚拟筛选技术在黑色素生成抑制剂研发中的应用进展,为探索黑色素生成抑制剂先导化合物提供参考。

Cenozoic plants from Tibet:An extraordinary decade of discovery,understanding and implications

Plant fossils play an important role in understanding landscape evolution across the Tibetan Region,as well as plant diversity across wider eastern Asia.Within the last decade or so,paleobotanical investigations within the Tibet Region have led to a paradigm shift in our understanding of how the present plateau formed and how this affected the regional climate and biota.This is because:(1)Numerous new taxa have been reported.Of all the Cenozoic records of new plant fossil species reported from the Tibet(Xizang)Autonomous Region 45 out of 63(70%)were documented after 2010.Among these,many represent the earliest records from Asia,or in some cases worldwide,at the genus or family level.(2)These fossils show that during the Paleogene,the region now occupied by the Tibetan Plateau was a globally significant floristic exchange hub.Based on paleobiogeographic studies,grounded by fossil evidence,there are four models of regional floristic migration and exchange,i.e.,into Tibet,out of Tibet,out of India and into/out of Africa.(3)Plant fossils evidence the asynchronous formation histories for different parts of the Tibetan Plateau.During most of the Paleogene,there was a wide east-west trending valley with a subtropical climate in central Tibet bounded by high(>4 km)mountain systems,but that by the early Oligocene the modern high plateau had begun to form by the rise of the valley floor.Paleoelevation reconstructions using radiometrically-dated plant fossil assemblages in southeastern Tibet show that by the earliest Oligocene southeastern Tibet(including the Hengduan Mountains)had reached its present elevation.(4)The coevolution between vegetation,landform and paleoenvironment is evidenced by fossil records from what is now the central Tibetan Plateau.From the Paleocene to Pliocene,plant diversity transformed from that of tropical,to subtropical forests,through warm to cool temperate woodland and eventually to deciduous shrubland in response to landscape evolution from a seasonally humid lowland valley,to a high and dry plateau.(5)Advanced multidisciplinary technologies and novel ideas applied to paleobotanical material and paleoenvironmental reconstructions,e.g.,fluorescence microscopy and paleoclimatic models,have been essential for interpreting Cenozoic floras on the Tibetan Region.However,despite significant progress investigating Cenozoic floras of the Tibetan Region,fossil records across this large region remain sparse,and for a better understanding of regional ecosystem dynamics and management more paleobotanical discoveries and multidisciplinary studies are required.

A Study on the Privatization Decisions of China Concepts Stock Based on the Tax Shield Effect

In this paper, we construct a company value model based on the tax shield effect for overseas listing and privatization scenarios. The trade-off process of privatization decisions is simulated in the context of China concept stock companies’ reality. The results indicate that the value of tax shields, the degree of undervaluation, the ability to obtain cash flows, the risk of short selling, the cost of listing transactions, and fraud penalties are critical factors influencing the choice of privatization. The company value analysis shows that tax shield effect positively affects the probability of privatization. Furthermore, the weaker the ability of a company to obtain cash flow when listed overseas, the lower the WACC, the higher the risk of being shorted, and the higher the cost of listing transactions, the higher the probability that a company will choose to go private. Finally, numerical simulations are adopted to validate the validity of the theoretical model and the findings using SINA’s privatization as a case study. The findings can provide academic guidance and a decision-making basis on trading arrangements for CCS companies.

横断山南段上新世的植被多样性与分布格局

横断山南段复杂的地形地貌和多样的气候环境造就了高度丰富的植被多样性。这种植被多样性的演化与形成是植物学、生态学等领域共同关注的科学问题,而植物化石是回答这一科学问题的重要媒介。本文基于横断山南段的9个上新世化石植物群,根据其植物组成和优势成分,分析其所代表的植被类型,总结了该地区上新世的植被多样性与空间分布,并结合古环境研究资料,探讨该地区植被多样性的兴起,植被分布格局的形成,及其与环境变迁之间的关联。结果显示,横断山南段在上新世时期已经具有了多种植被类型,包括亚热带常绿阔叶林、亚热带落叶阔叶林、硬叶常绿阔叶林、针阔叶混交林、灌丛草地等,体现了丰富的植被多样性;植被类型从南面的偏热性植被向北面的偏温性植被逐渐转变,反映了当时随纬度变化的海拔梯度,植被类型与分布呈现出与现在高度相似的格局。同时,小范围内也具有适应于不同气候的植被类型,反映了当地较大的海拔落差,可能与高大山体的存在有着密切关联。我们推测,横断山南段现在丰富的植被多样性和随纬度变化的植被面貌最晚在上新世就已基本形成,但形成时间是否更早则需要更多、更老化石植物群的发现与研究。

Evolution of stomatal and trichome density of the Quercus delavayi complex since the late Miocene

A fossil oak species,Quercus tenuipilosa Q.Hu et Z.K.Zhou,is reported from the upper Pliocene Ciying Formation in Kunming,Yunnan Province,southwestern China.The establishment of this species is based on detailed morphologic and cuticular investigations.The fossil leaves are elliptic,with serrate margins on the apical half.The primary venation is pinnate,and the major secondary venation is craspedodromous.The tertiary veins are opposite or alternate-opposite percurrent with two branches.The stomata are anomocytic,occurring only on the abaxial epidermis.The trichome bases are unicellular or multicellular.The new fossil species shows the closest affinity with theextant Q.delavayi and the late Miocene Q.praedelavayi Y.W.Xing et Z.K.Zhou from the Xiaolongtan Formation of the Yunnan Province.All three species share similar leaf morphology,but differ with respect to trichome base and stomatal densities.Q.tenuipilosa.Q.praedelavayi,and Q.delavayi can be considered to constitute the Q.delavayi complex.Since the late Miocene,a gradual reduction in trichome base density has occurred in this complex.This trend is the opposite of that of precipitation,indicating that increased trichome density is not an adaptation to dry environments.The stomatal density(SD)of the Q.delavayi complex was the highest during the late Miocene,declined in the late Pliocene,and then increased during the present epoch.These values show an inverse relationship with atmospheric CO_2 concentrations,suggesting that the SD of the Q.delavayi complex may be a useful proxy for reconstruction of paleo-CO_2 concentrations.