The Sulfolobus acidocaldarius S-layer is composed of two main proteins: SlaA, which forms the ordered structure of the S-layer matrix, and SlaB, which supports and anchors the S-layer into the tetraether lipid membrane. While SlaA has previously been purified by exploiting its thermotolerance and high resistance to detergents, SlaB has resisted isolation, particularly from the cell membrane. Removal of proteins other than those of the S-layer is especially difficult if large batch-scale culture volumes are unavailable. Here, we describe a benchtop-scale protocol for the purification of SlaA from S. acidocaldarius, enabling isolation of SlaB using size exclusion chromatography (gel filtration). Using this protocol, we were able to identify for the first time tetraether lipids strongly attached to SlaB via heat- and detergent-resistant interactions.
Dissecting the genetic basis of intraspecific variations in life history traits is essential to understand their evolution, notably for potential biocontrol agents. Such variations are observed in the endoparasitoid Cotesia typhae (Hymenoptera: Braconidae), specialized on the pest Sesamia nonagrioides (Lepidoptera: Noctuidae). Previously, we identified two strains of C. typhae that differed significantly for life history traits on an allopatric host population. To investigate the genetic basis underlying these phenotypic differences, we used a quantitative trait locus (QTL) approach based on restriction site‐associated DNA markers. The characteristic of C. typhae reproduction allowed us generating sisters sharing almost the same genetic content, named clonal sibship. Crosses between individuals from the two strains were performed to generate F2 and F8 recombinant CSS. The genotypes of 181 clonal sibships were determined as well as the phenotypes of the corresponding 4,000 females. Informative markers were then used to build a high‐quality genetic map. These 465 markers spanned a total length of 1,300 cM and were organized in 10 linkage groups which corresponded to the number of C. typhae chromosomes. Three QTLs were detected for parasitism success and two for offspring number, while none were identified for sex ratio. The QTLs explained, respectively, 27.7% and 24.5% of the phenotypic variation observed. The gene content of the genomic intervals was investigated based on the genome of C. congregata and revealed 67 interesting candidates, as potentially involved in the studied traits, including components of the venom and of the symbiotic virus (bracovirus) shown to be necessary for parasitism success in related wasps. 相似文献
Epigenetic histone trimethylation on lysine 9 (H3K9me3) represents a major molecular signal for genome stability and gene silencing conserved from worms to man. However, the functional role of the H3K9 trimethylases SUV39H1/2 in mammalian tissue homeostasis remains largely unknown. Here, we use a spontaneous dog model with monogenic inheritance of a recessive SUV39H2 loss-of-function variant and impaired differentiation in the epidermis, a self-renewing tissue fueled by stem and progenitor cell proliferation and differentiation. Our results demonstrate that SUV39H2 maintains the stem and progenitor cell pool by restricting fate conversion through H3K9me3 repressive marks on gene promoters encoding components of the Wnt/p63/adhesion axis. When SUV39H2 function is lost, repression is relieved, and enhanced Wnt activity causes progenitor cells to prematurely exit the cell cycle, a process mimicked by pharmacological Wnt activation in primary canine, human, and mouse keratinocytes. As a consequence, the stem cell growth potential of cultured SUV39H2-deficient canine keratinocytes is exhausted while epidermal differentiation and genome stability are compromised. Collectively, our data identify SUV39H2 and potentially also SUV39H1 as major gatekeepers in the delicate balance of progenitor fate conversion through H3K9me3 rate-limiting road blocks in basal layer keratinocytes. 相似文献
Eco-evolutionary dynamics can mediate species and community responses to habitat warming and fragmentation, two of the largest threats to biodiversity and ecosystems. The eco-evolutionary consequences of warming and fragmentation are typically studied independently, hindering our understanding of their simultaneous impacts. Here, we provide a new perspective rooted in trade-offs among traits for understanding their eco-evolutionary consequences. On the one hand, temperature influences traits related to metabolism, such as resource acquisition and activity levels. Such traits are also likely to have trade-offs with other energetically costly traits, like antipredator defences or dispersal. On the other hand, fragmentation can influence a variety of traits (e.g. dispersal) through its effects on the spatial environment experienced by individuals, as well as properties of populations, such as genetic structure. The combined effects of warming and fragmentation on communities should thus reflect their collective impact on traits of individuals and populations, as well as trade-offs at multiple trophic levels, leading to unexpected dynamics when effects are not additive and when evolutionary responses modulate them. Here, we provide a road map to navigate this complexity. First, we review single-species responses to warming and fragmentation. Second, we focus on consumer–resource interactions, considering how eco-evolutionary dynamics can arise in response to warming, fragmentation, and their interaction. Third, we illustrate our perspective with several example scenarios in which trait trade-offs could result in significant eco-evolutionary dynamics. Specifically, we consider the possible eco-evolutionary consequences of (i) evolution in thermal performance of a species involved in a consumer–resource interaction, (ii) ecological or evolutionary changes to encounter and attack rates of consumers, and (iii) changes to top consumer body size in tri-trophic food chains. In these scenarios, we present a number of novel, sometimes counter-intuitive, potential outcomes. Some of these expectations contrast with those solely based on ecological dynamics, for example, evolutionary responses in unexpected directions for resource species or unanticipated population declines in top consumers. Finally, we identify several unanswered questions about the conditions most likely to yield strong eco-evolutionary dynamics, how better to incorporate the role of trade-offs among traits, and the role of eco-evolutionary dynamics in governing responses to warming in fragmented communities. 相似文献
Rhizoliths, that is, roots fossilized by secondary carbonates, have been known for ages and are increasingly used for paleoenvironmental reconstructions. However, knowledge about their formation mechanisms remains limited. This study reports the mineralogical and chemical characterization of rhizoliths at different stages of mineralization and fossilization in the Late Pleistocene loess–paleosol sequence of Nussloch (SW Germany). Scanning electron microscopy coupled with elemental mapping and 13C solid‐state nuclear magnetic resonance were used to concomitantly characterize the mineral and organic matter of the rhizoliths. These joint analyses showed for the first time that large rhizoliths are not necessarily remains of single large roots but consist of numerous microrhizoliths as remains of fine roots, formed mainly by calcium carbonates with only low amounts of Mg and Si. They further revealed that the precipitation of secondary carbonates occurs not only around, but also within the plant root and that fossilization leads to the selective preservation of recalcitrant root biopolymers—lignin and suberin. The precipitation of secondary carbonates was observed to occur first around fine roots, the epidermis acting as a first barrier, and then within the root, within the cortex cells, and even sometimes around the phloem and within the xylem. This study suggests that the calcification of plant roots starts during the lifetime of the plant and continues after its death. This has to be systematically investigated to understand the stratigraphic context before using (micro)rhizoliths for paleoenvironmental reconstructions in terrestrial sediments. 相似文献