Coordinated evolution of brain size,structure, and eye size in Trinidadian killifish

Brain size, brain architecture, and eye size vary extensively in vertebrates. However, the extent to which the evolution of these components is intricately connected remains unclear. Trinidadian killifish, Anablepsoides hartii, are found in sites that differ in the presence and absence of large predatory fish. Decreased rates of predation are associated with evolutionary shifts in brain size; males from sites without predators have evolved a relatively larger brain and eye size than males from sites with predators. Here, we evaluated the extent to which the evolution of brain size, brain structure, and eye size covary in male killifish. We utilized wild‐caught and common garden‐reared specimens to determine whether specific components of the brain have evolved in response to differences in predation and to determine if there is covariation between the evolution of brain size, brain structure, and eye size. We observed consistent shifts in brain architecture in second generation common garden reared, but not wild caught preserved fish. Male killifish from sites that lack predators exhibited a significantly larger telencephalon, optic tectum, cerebellum, and dorsal medulla when compared with fish from sites with predators. We also found positive connections between the evolution of brain structure and eye size but not between overall brain size and eye size. These results provide evidence for evolutionary covariation between the components of the brain and eye size. Such results suggest that selection, directly or indirectly, acts upon specific regions of the brain, rather than overall brain size, to enhance visual capabilities.     

Patterns in root traits of woody species hosting arbuscular and ectomycorrhizas: implications for the evolution of belowground strategies

Root traits vary enormously among plant species but we have little understanding of how this variation affects their functioning. Of central interest is how root traits are related to plant resource acquisition strategies from soil. We examined root traits of 33 woody species from northeastern US forests that form two of the most common types of mutualisms with fungi, arbuscular mycorrhizas (AM) and ectomycorrhizas (EM). We examined root trait distribution with respect to plant phylogeny, quantifying the phylogenetic signal (K statistic) in fine root morphology and architecture, and used phylogenetically independent contrasts (PICs) to test whether taxa forming different mycorrhizal associations had different root traits. We found a pattern of species forming roots with thinner diameters as species diversified across time. Given moderate phylogenetic signals (K = 0.44–0.68), we used PICs to examine traits variation among taxa forming AM or EM, revealing that hosts of AM were associated with lower branching intensity (r_PIC = −0.77) and thicker root diameter (r_PIC = −0.41). Because EM evolved relatively more recently and intermittently across plant phylogenies, significant differences in root traits and colonization between plants forming AM and EM imply linkages between the evolution of these biotic interactions and root traits and suggest a history of selection pressures, with trade-offs for supporting different types of associations. Finally, across plant hosts of both EM and AM, species with thinner root diameters and longer specific root length (SRL) had less colonization (r_PIC = 0.85, −0.87), suggesting constraints on colonization linked to the evolution of root morphology.     

中国水青冈属 （壳斗科） 叶结构及分类学意义

叶结构对壳斗科(Fagaceae)现存植物和化石的鉴定具有重要意义。通过对水青冈属5种植物叶结构特征进行细致的研究,结果发现水青冈属植物叶脉有羽状弓形脉、羽状半达缘脉两种类型;三级脉有波状对生贯穿、互生贯穿及混合贯穿三种类型;小脉缺失、简单无分支或一次分支;脉间区发育良好,网眼有三边形、四边形和五边形三种类型,排列规则;具齿种类叶齿由齿主脉和齿侧脉构成,齿侧脉环状。研究结果表明水青冈属二级脉与更高级脉序形成的结构稳定且存在种间差异,具重要分类学价值。基于水青冈属叶结构特征观察结果,本次研究编制了水青冈属植物的分种检索表;参照已有研究结果并结合重要外部形态学特征,编制了壳斗科相关类群分属检索表。     

The evolutionary relationship of the domain architectures in the RhoGEF-containing proteins

Domain insertions and deletions lead to variations in the domain architectures of the proteins from their common ancestor. In this work, we investigated four groups of the RhoGEF-containing proteins from different organisms with domain architectures RhoGEF-PH-SH3, SH3-RhoGEF-PH, RhoGEF-PH, and SH3-RhoGEF defined in the Pfam database. The phylogenetic trees were constructed using each individual domain and/or the combinations of all the domains. The phylogenetic analysis suggests that RhoGEF-PH-SH3 and SH3-RhoGEF-PH might have evolved from RhoGEF-PH through the insertion of SH3 independently, while SH3- RhoGEF of proteins in fruit fly might have evolved from SH3-RhoGEF-PH by the degeneration of PH domain.     

Quantitative genetic inheritance of morphological divergence in a lake-stream stickleback ecotype pair: implications for reproductive isolation

Ecological selection against hybrids between populations occupying different habitats might be an important component of reproductive isolation during the initial stages of speciation. The strength and directionality of this barrier to gene flow depends on the genetic architecture underlying divergence in ecologically relevant phenotypes. We here present line cross analyses of inheritance for two key foraging-related morphological traits involved in adaptive divergence between stickleback ecotypes residing parapatrically in lake and stream habitats within the Misty Lake watershed (Vancouver Island, Canada). One main finding is the striking genetic dominance of the lake phenotype for body depth. Selection associated with this phenotype against first- and later-generation hybrids should therefore be asymmetric, hindering introgression from the lake to the stream population but not vice versa. Another main finding is that divergence in gill raker number is inherited additively and should therefore contribute symmetrically to reproductive isolation. Our study suggests that traits involved in adaptation might contribute to reproductive isolation qualitatively differently, depending on their mode of inheritance.     

Structural dynamics and epigenetic modifications of Hoxc loci along the anteroposterior body axis in developing mouse embryos

Hox genes are organized as clusters and specify regional identity along the anteroposterior body axis by sequential expression at a specific time and region during embryogenesis. However, the precise mechanisms underlying the sequential spatio-temporal, collinear expression pattern of Hox genes are not fully understood. Since epigenetic modifications such as chromatin architecture and histone modifications have become crucial mechanisms for highly coordinated gene expressions, we examined such modifications. E14.5 mouse embryos were dissected into three parts along the anteroposterior axis: brain, trunk-anterior, and trunk-posterior. Then, structural changes and epigenetic modifications were analyzed along the Hoxc cluster using chromosome conformation capture and chromatin immunoprecipitation-PCR methods. Hox non-expressing brain tissues had more compact, heterochromatin-like structures together with the strong repressive mark H3K27me3 than trunk tissues. In the trunk, however, a more loose euchromatin-like topology with a reduced amount of H3K27me3 modifications were observed along the whole cluster, regardless of their potency in gene activation. The active mark H3K4me3 was rather closely associated with the collinear expression of Hoxc genes; at trunk-anterior tissues, only 3' anterior Hoxc genes were marked by H3K4me3 upon gene activation, whereas whole Hoxc genes were marked by H3K4me3 and showed expression in trunk-posterior tissues. Altogether, these results indicated that loosening of the chromatin architecture and removing H3K27me3 were not sufficient for, but rather the concomitant acquisition of H3K4me3 drove the collinear expression of Hoxc genes.     

外源NO对铜胁迫下番茄幼苗根系构型及其超微结构的影响

采用营养液水培的方法,以“改良毛粉802F1”番茄为材料,硝普钠（sodiumnitroprusside,sNP）为一氧化氮（N0）供体,研究外源N0对铜胁迫下番茄幼苗根系构型及其超微结构的影响。结果表明,50μmol·L-1的铜胁迫下,外施100μmol·L-1 SNP能够显著增加番茄幼苗植株的生物量、株高和茎粗,提高根系活力,改善根系构型中的根长度、根平均直径、根表面积和根体积,缓解番茄幼苗亚细胞结构（细胞核、线粒体、叶绿体、液泡、核膜）的改变,维持番茄幼苗组织结构的稳定,减缓铜胁迫对植株生长的抑制作用,添加NO清除剂牛血红蛋白后,能显著消除NO的缓解效果。