| 1. |
- Alfoeldi, Jessica, et al.
(författare)
-
The genome of the green anole lizard and a comparative analysis with birds and mammals
- 2011
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 477:7366, s. 587-591
-
Tidskriftsartikel (refereegranskat)abstract
- The evolution of the amniotic egg was one of the great evolutionary innovations in the history of life, freeing vertebrates from an obligatory connection to water and thus permitting the conquest of terrestrial environments(1). Among amniotes, genome sequences are available for mammals and birds(2-4), but not for non-avian reptiles. Here we report the genome sequence of the North American green anole lizard, Anolis carolinensis. We find that A. carolinensis microchromosomes are highly syntenic with chicken microchromosomes, yet do not exhibit the high GC and low repeat content that are characteristic of avian microchromosomes(2). Also, A. carolinensis mobile elements are very young and diverse-more so than in any other sequenced amniote genome. The GC content of this lizard genome is also unusual in its homogeneity, unlike the regionally variable GC content found in mammals and birds(5). We describe and assign sequence to the previously unknown A. carolinensis X chromosome. Comparative gene analysis shows that amniote egg proteins have evolved significantly more rapidly than other proteins. An anole phylogeny resolves basal branches to illuminate the history of their repeated adaptive radiations.
|
|
| 2. |
- Charpentier, Emmanuelle, et al.
(författare)
-
Novel cassette-based shuttle vector system for Gram-positive bacteria.
- 2004
-
Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 70:10, s. 6076-6085
-
Tidskriftsartikel (refereegranskat)abstract
- Our understanding of staphylococcal pathogenesis depends on reliable genetic tools for gene expression analysis and tracing of bacteria. Here, we have developed and evaluated a series of novel versatile Escherichia coli-staphylococcal shuttle vectors based on PCR-generated interchangeable cassettes. Advantages of our module system include the use of (i) staphylococcal low-copy-number, high-copy-number, thermosensitive and theta replicons and selectable markers (choice of erythromycin, tetracycline, chloramphenicol, kanamycin, or spectinomycin); (ii) an E. coli replicon and selectable marker (ampicillin); and (iii) a staphylococcal phage fragment that allows high-frequency transduction and an SaPI fragment that allows site-specific integration into the Staphylococcus aureus chromosome. The staphylococcal cadmium-inducible P(cad)-cadC and constitutive P(blaZ) promoters were designed and analyzed in transcriptional fusions to the staphylococcal beta-lactamase blaZ, the Vibrio fischeri luxAB, and the Aequorea victoria green fluorescent protein reporter genes. The modular design of the vector system provides great flexibility and variety. Questions about gene dosage, complementation, and cis-trans effects can now be conveniently addressed, so that this system constitutes an effective tool for studying gene regulation of staphylococci in various ecosystems.
|
|
| 3. |
- Mangold, Monika, et al.
(författare)
-
Synthesis of group A streptococcal virulence factors is controlled by a regulatory RNA molecule.
- 2004
-
Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 53:5, s. 1515-1527
-
Tidskriftsartikel (refereegranskat)abstract
- The capacity of pathogens to cause disease depends strictly on the regulated expression of their virulence factors. In this study, we demonstrate that the untranslated mRNA of the recently described streptococcal pleiotropic effect locus (pel), which incidentally contains sagA, the structural gene for streptolysin S, is an effector of virulence factor expression in group A beta-haemolytic streptococci (GAS). Our data suggest that the regulation by pel RNA occurs at both transcriptional (e.g. emm, sic, nga) and post-transcriptional (e.g. SpeB) levels. We could exclude the possibility that the pel phenotype was linked to a polar effect on downstream genes (sagB-I). Remarkably, the RNA effector is regulated in a growth phase-dependent fashion and we provide evidence that pel RNA expression is induced by conditioned media.
|
|
| 4. |
- Zhang, Quan, et al.
(författare)
-
Changes in photosynthesis and soil moisture drive the seasonal soil respiration-temperature hysteresis relationship
- 2018
-
Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 0168-1923 .- 1873-2240. ; 259, s. 184-195
-
Tidskriftsartikel (refereegranskat)abstract
- In nearly all large-scale terrestrial ecosystem models, soil respiration is represented as a function of soil temperature. However, the relationship between soil respiration and soil temperature is highly variable across sites and there is often a pronounced hysteresis in the soil respiration-temperature relationship over the course of the growing season. This phenomenon indicates the importance of biophysical factors beyond just temperature in controlling soil respiration. To identify the potential mechanisms of the seasonal soil respiration-temperature hysteresis, we developed a set of numerical models to demonstrate how photosynthesis, soil moisture, and soil temperature, alone and in combination, affect the hysteresis relationship. Then, we used a variant of the model informed by observations of soil respiration, soil temperature, photosynthesis, and soil moisture from multiple mesic and semi-arid ecosystems to quantify the frequency of hysteresis and identify its potential controls. We show that the hysteresis can result from the seasonal cycle of photosynthesis (which supplies carbon to rhizosphere respiration), and soil moisture (which limits heterotrophic respiration when too low or too high). Using field observations of soil respiration, we found evidence of seasonal hysteresis in 9 out of 15 site-years across 8 diverse biomes. Specifically, clockwise hysteresis occurred when photosynthesis preceded seasonal soil temperature and counterclockwise hysteresis occurred when photosynthesis lagged soil temperature. We found that across all sites, much of the respiration-temperature lag was explained by the decoupling of photosynthesis and temperature, highlighting the importance of recently assimilated carbon to soil respiration. An analysis of observations from 129 FLUXNET sites revealed that time lags between gross primary productivity (a proxy for canopy photosynthesis) and soil temperature were common phenomena, which would tend to drive counterclockwise hysteresis at low-latitude sites and clockwise hysteresis at high-latitude sites. Collectively, our results show that incorporating photosynthesis and soil moisture in the standard exponential soil respiration-temperature model (i.e., Q(10) model) improves the explanatory power of models at local scales.
|
|
| 5. |
- Zhang, Quan, et al.
(författare)
-
Response of ecosystem intrinsic water use efficiency and gross primary productivity to rising vapor pressure deficit
- 2019
-
Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 14:7
-
Tidskriftsartikel (refereegranskat)abstract
- Elevated vapor pressure deficit (VPD) due to drought and warming is well-known to limit canopy stomatal and surface conductance, but the impacts of elevated VPD on ecosystem gross primary productivity (GPP) are less clear. The intrinsic water use efficiency (iWUE), defined as the ratio of carbon (C) assimilation to stomatal conductance, links vegetation C gain and water loss and is a key determinant of how GPP will respond to climate change. While it is well-established that rising atmospheric CO2 increases ecosystem iWUE, historic and future increases in VPD caused by climate change and drought are often neglected when considering trends in ecosystem iWUE. Here, we synthesize long-term observations of C and water fluxes from 28 North American FLUXNET sites, spanning eight vegetation types, to demonstrate that ecosystem iWUE increases consistently with rising VPD regardless of changes in soil moisture. Another way to interpret this result is that GPP decreases less than surface conductance with increasing VPD. We also project how rising VPD will impact iWUE into the future. Results vary substantially from one site to the next; in a majority of sites, future increases in VPD (RCP 8.5, highest emission scenario) are projected to increase iWUE by 5%-15% by 2050, and by 10%-35% by the end of the century. The increases in VPD owing to elevated global temperatures could be responsible for a 0.13% year(-1) increase in ecosystem iWUE in the future. Our results highlight the importance of considering VPD impacts on iWUE independently of CO2 impacts.
|
|
