毛竹APX基因系统进化与表达分析

抗坏血酸过氧化物酶(aseorbate peroxidase, APX)是植物活性氧代谢中重要的抗氧化酶之一,尤其是叶绿体中清除H₂O₂的关键酶,也是维生素C代谢的主要酶类。该文基于生物信息学方法,利用毛竹的基因组及转录组数据鉴定毛竹中的APX基因家族成员,并对其编码的蛋白基本理化性质、基因结构、启动子元件、系统进化及共线性关系、重复串联基因、GO注释及表达模式进行综合分析,共鉴定出21种编码APX的基因。结果表明:(1)PeAPX基因家族成员多为不稳定疏水蛋白,基因结构、基序及结构域相对较为保守,大多数APX基因具有高度保守的内含子模式。(2)系统进化关系显示毛竹APX基因与水稻APX基因有着较高的同源性关系,PeAPX具有较高的进化保守性。(3)Ka/Ks分析表明PeAPX基因都经历了纯化选择压力,此外在每个APX基因的启动子序列中发现有许多与应激反应和植物激素相关的顺式作用元件,结合表达量分析,表明毛竹APX基因在毛竹生长发育中起着正向促进作用。该研究为进一步了解毛竹APX基因家族基本功能及其抗氧化机制提供了一定的参考,为毛竹APX基因功能的深层次鉴定提供了重要依据。     

Evolutionary heritage shapes tree distributions along an Amazon‐to‐Andes elevation gradient

Understanding how evolutionary constraints shape the elevational distributions of tree lineages provides valuable insight into the future of tropical montane forests under global change. With narrow elevational ranges, high taxonomic turnover, frequent habitat specialization, and exceptional levels of endemism, tropical montane forests and trees are predicted to be highly sensitive to environmental change. Using plot census data from a gradient traversing > 3,000 m in elevation on the Amazonian flank of the Peruvian Andes, we employ phylogenetic approaches to assess the influence of evolutionary heritage on distribution trends of trees at the genus‐level. We find that closely related lineages tend to occur at similar mean elevations, with sister genera pairs occurring a mean 254 m in elevation closer to each other than the mean elevational difference between non‐sister genera pairs. We also demonstrate phylogenetic clustering both above and below 1,750 m a.s.l, corresponding roughly to the cloud‐base ecotone. Belying these general trends, some lineages occur across many different elevations. However, these highly plastic lineages are not phylogenetically clustered. Overall, our findings suggest that tropical montane forests are home to unique tree lineage diversity, constrained by their evolutionary heritage and vulnerable to substantial losses under environmental changes, such as rising temperatures or an upward shift of the cloud‐base.     

Plant–plant facilitation increases with reduced phylogenetic relatedness along an elevation gradient

Environmental conditions can modify the intensity and sign of ecological interactions. The stress gradient hypothesis (SGH) predicts that facilitation becomes more important than competition under stressful conditions. To properly test this hypothesis, it is necessary to account for all (not a subset of) interactions occurring in the communities and consider that species do not interact at random but following a specific pattern. We aim to assess elevational changes in facilitation, in terms of species richness, frequency and intensity of the interaction as a function of the evolutionary relatedness between nurses and their associated species. We sampled nurse and their facilitated plant species in two 1000–2000 m. elevation gradients in Mediterranean Chile where low temperature imposes a mortality filter on seedlings. We first estimated the relative importance of facilitation as a mechanism adding new species to communities distributed along these gradients. We then tested whether the frequency and intensity of facilitation increases with elevation, taking into account the evolutionary relatedness of the nurse species and the facilitated species. We found that nurses increase the species richness of the community by up to 35%. Facilitative interactions are more frequent than competitive interactions (56% versus 44%) and facilitation intensity increased with elevation for interactions involving distantly related lineages. Our results highlight the importance of including an evolutionary dimension in the study of facilitation to have a clearer picture of the mechanisms enabling species to coexist and survive under stressful conditions. This knowledge is especially relevant to conserve vulnerable and threatened communities facing new climate scenarios, such as those located in Mediterranean-type ecosystems.     

Congruent spatial patterns of species richness and phylogenetic diversity in karst flora: Case study of Primulina (Gesneriaceae)

The karst landform in southern China is renowned for its high levels of species diversity and endemism. Globally, karst ecosystems are under threat from unsustainable anthropogenic disturbance and climate changes and are among the most threatened ecosystems worldwide. In this study, we used the typical karst endemic genus in southern China, Primulina Hance, as a model to identify areas within the karst landform with high diversity and to investigate congruence between phylogenetic and species‐based measures of diversity. Using phylogenetic information and species distribution data, we measured geographical patterns of diversity with four metrics: species richness (SR), corrected weighted endemism (CWE), phylogenetic diversity (PD), and phylogenetic endemism (PE). Our results revealed a high spatial congruence among SR, PD, and PE, with hotspot areas identified in the Nanling Mountains (i.e., north Guangdong and northeast Guangxi) and southeast Yungui Plateau (i.e., north and southwest Guangxi), whereas the hotspots of CWE are comparatively uniform throughout the geographic extent. The categorical analysis of neo‐ and paleoendemism identified a pattern of mixed neo‐ and paleoendemism in numerous grid cells, suggesting that karst areas in southern China have acted as both “museums” and “cradles” of plant evolution. Conservation gap analysis of hotspots revealed that the majority of prioritized hotspots (>90%) of the genus are outside of protected areas, therefore indicating the limited effectiveness of national nature reserves for the karst flora. Overall, our results suggest that the karst flora merits more conservation attention and SR can be an effective surrogate to capture PD in conservation planning.     

巴尔通体在滇西南蝙蝠中高度流行并具有丰富的遗传变异特征

蝙蝠是很多病原微生物的自然宿主, 全球多项研究表明蝙蝠是巴尔通体(Bartonella species)的主要宿主。为了解滇西南地区蝙蝠中巴尔通体的流行特征, 我们于2015-2017年间在云南省4个地区应用网捕法捕获蝙蝠3种305只。经种类鉴定后采集肝脾组织, 提取核酸, 通过TaqMan实时荧光定量PCR方法检测巴尔通体的tmRNA基因ssrA, 并进行测序鉴定和系统发育分析。结果发现172只蝙蝠检出该基因, 总感染率为56.4%; 其中临沧、西双版纳、保山和瑞丽4个采样点的蝙蝠感染率分别为50.0% (22/44)、61.7% (29/47)、62.1% (18/29)和55.7% (103/185)。中菊头蝠(Rhinolophus affinis)、小菊头蝠(R. blythi)和棕果蝠(Rousettus leschenaultii)的感染率分别为50.0% (22/44)、62.1% (18/29)和56.9% (132/232), 差异没有统计学意义(χ² = 1.135, P = 0.567), 表明巴尔通体在云南当地的蝙蝠种群中高度流行。定量PCR扩增产物2次扩增后测序获得37个巴尔通体ssrA序列, 属于10个系统发育分支, 其中1个为伊丽莎白巴尔通体(B. elizabethae)、特利波契巴尔通体(B. tribocorum)和克拉斯诺夫巴尔通体(B. krasnovii)的近缘种。其余序列与已知巴尔通体距离较远, 与亚洲、欧洲和美洲等其他地域来源于蝙蝠的巴尔通体近缘。遗传多样性分析显示, ssrA基因的核苷酸多样性指数(π)为0.11381 ± 0.00928, 基因型多样性指数(Hd)为0.985 ± 0.010, 形成29个基因型(单倍型), 说明云南蝙蝠巴尔通体具有丰富的遗传多样性。通过对本研究标本与全球相关序列的系统发育网络重建, 分析全球蝙蝠巴尔通体的地理和宿主分布特征, 可以看出巴尔通体与蝙蝠之间存在显著的宿主特异性关联。因此可初步确定蝙蝠-巴尔通体具有协同进化特征, 同时受到地理隔离的影响。