The California Hotspots Project: identifying regions of rapid diversification of mammals

The high rate of anthropogenic impact on natural systems mandates protection of the evolutionary processes that generate and sustain biological diversity. Environmental drivers of diversification include spatial heterogeneity of abiotic and biotic agents of divergent selection, features that suppress gene flow, and climatic or geological processes that open new niche space. To explore how well such proxies perform as surrogates for conservation planning, we need first to map areas with rapid diversification -'evolutionary hotspots'. Here we combine estimates of range size and divergence time to map spatial patterns of neo-endemism for mammals of California, a global biodiversity hotspot. Neo-endemism is explored at two scales: (i) endemic species, weighted by the inverse of range size and mtDNA sequence divergence from sisters; and (ii) as a surrogate for spatial patterns of phenotypic divergence, endemic subspecies, again using inverse-weighting of range size. The species-level analysis revealed foci of narrowly endemic, young taxa in the central Sierra Nevada, northern and central coast, and Tehachapi and Peninsular Ranges. The subspecies endemism-richness analysis supported the last four areas as hotspots for diversification, but also highlighted additional coastal areas (Monterey to north of San Francisco Bay) and the Inyo Valley to the east. We suggest these hotspots reflect the major processes shaping mammal neo-endemism: steep environmental gradients, biotic admixture areas, and areas with recent geological/climate change. Anthropogenic changes to both environment and land use will have direct impacts on regions of rapid divergence. However, despite widespread changes to land cover in California, the majority of the hotspots identified here occur in areas with relatively intact ecological landscapes. The geographical scope of conserving evolutionary process is beyond the scale of any single agency or nongovernmental organization. Choosing which land to closely protect and/or purchase will always require close coordination between agencies.     

Generation of transgenic chickens that produce bioactive human granulocyte-colony stimulating factor

We report here the generation of transgenic chickens that produce human granulocyte-colony stimulating factor (hG-CSF) using replication-defective Moloney murine leukemia virus (MoMLV)-based vectors packaged with vesicular stomatitis virus G glycoprotein (VSV-G). The recombinant retrovirus was injected beneath the blastoderm of nonincubated chicken embryos (stage X). Out of 140 injected eggs, 17 chicks hatched after 21 days of incubation and all hatched chicks were found to express vector-encoded hG-GSF gene. The biological activity of the recombinant hG-CSF was significantly higher than its commercially derived E. coli-derived counterpart. Successful germline transmission of the transgene was also confirmed in G(1) transgenic chicks produced from the cross of Go transgenic roosters with nontransgenic hens, but most of the G(1) progeny were dead within 1 month of hatching.     

Enhanced Expressions of Arginine Vasopressin (Avp) in the Hypothalamic Paraventricular and Supraoptic Nuclei of Type 2 Diabetic Rats

Arginine vasopressin (AVP) is known to a neuropeptide that plays important roles in water conservation, sodium homeostasis, and in the regulation of serum osmolality. Several studies have reported that the elevated AVP level is related with diabetes mellitus as an acute or chronic stressor using type 1 diabetes mellitus animal models. However, it is unclear as to how the immunoreactivity and protein level of AVP in the brain is regulated in animal models of type 2 diabetes mellitus. In the present study, Zucker diabetic fatty (ZDF) rats were employed as a type 2 diabetes mellitus model and were compared with Zucker lean control (ZLC) rats with respect to AVP protein expression. Furthermore, in order to verify the regulation of AVP expression before and after the onset of diabetes mellitus, pre-diabetic rats (4 week-old) and obese-diabetic rats (12 week-old) were used. Blood glucose levels and water consumption were also measured and the results showed significantly high in 12 week-old ZDF than any other groups. AVP expression levels in the paraventricular nucleus and supraoptic nucleus were found to be significantly higher in 12 week-old ZDF rats than in 12 week-old ZLC rats and than in 4 week-old rats by immunostaining and western blotting. Enhanced expression of AVP in these animals may be associated with type 2 diabetes mellitus. Special issue article in honor of George Fink.     

Age-related Differentiation in Newly Generated DCX Immunoreactive Neurons in the Subgranular Zone of the Gerbil Dentate Gyrus

In the present study, we investigated age-related changes of newborn neurons in the gerbil dentate gyrus using doublecortin (DCX), a marker of neuronal progenitors which differentiate into neurons in the brain. In the postnatal month 1 (PM 1) group, DCX immunoreactivity was detected in the subgranular zone of the dentate gyrus, but DCX immunoreactive neurons did not have fully developed processes. Thereafter, DCX immunoreactivity and its protein levels in the dentate gyrus were found to decrease with age. Between PM 3 and PM 18, DCX immunoreactive neuronal progenitors showed well-developed processes which projected to the granular layer of the dentate gyrus, but at PM 24, a few DCX immunoreactive neuronal progenitors were detected in the subgranular zone of the dentate gyrus. DCX protein level in the dentate gyrus at PM 1 was high, thereafter levels of DCX were decreased with time. The authors suggest that a decrease of DCX immunoreactivity and its protein level with age may be associated with aging processes in the hippocampal dentate gyrus.     

Seedling Growth and Heavy Metal Accumulation of Candidate Woody Species for Revegetating Korean Mine Spoils

Selecting plant species that can overcome harsh soil and microclimatic conditions and speed the recovery of degraded minelands remains a worldwide restoration challenge. This study evaluated the potential of three woody species and various organic and inorganic fertilization treatments for revegetating abandoned metalliferous mines in Korea. We compared survival, growth, and heavy metal uptake of species common to Korean minelands in two spoil types and a reference forest soil. Substrate type and fertilization both influenced seedling growth and metal concentrations substantially, but they had little effect on seedling survival. Fertilization increased the growth of all three species when grown in mine spoils but influenced the growth of seedlings grown in forest soil only marginally. Initial seedling survival and growth indicate that the study species can tolerate the heavy metal concentrations and other soil constraints of metalliferous spoil types. We estimate that plants can stabilize 2–22% of various heavy metals contained in spoil materials into plant biomass during 20 years of plantation growth. Combined with the erosion control and site amelioration benefits of mineland reforestation, stabilization of heavy metals in forest biomass justifies this treatment on abandoned Korean metalliferous mines.     

Mind bomb-1 is essential for intraembryonic hematopoiesis in the aortic endothelium and the subaortic patches

Intraembryonic hematopoiesis occurs at two different sites, the floor of the aorta and subaortic patches (SAPs) of the para-aortic splanchnopleura (P-Sp)/aorta-gonad-mesonephros (AGM) region. Notch1 and RBP-jκ are critical for the specification of hematopoietic stem cells (HSCs) in Notch signal-receiving cells. However, the mechanism by which Notch signaling is triggered from the Notch signal-sending cells to support embryonic hematopoiesis remains to be determined. We previously reported that Mind bomb-1 (Mib1) regulates Notch ligands in the Notch signal-sending cells (B. K. Koo, M. J. Yoon, K. J. Yoon, S. K. Im, Y. Y. Kim, C. H. Kim, P. G. Suh, Y. N. Jan, and Y. Y. Kong, PLoS ONE 2:e1221, 2007). Here, we show that intraembryonic hematopoietic progenitors were absent in the P-Sp of Mib1^−/− embryos, whereas they were partly preserved in the Tie2-cre; Mib1^f/f P-Sps, suggesting that Mib1 plays a role in the endothelium and the SAPs. Interestingly, dll1 and dll4/Jag1 are expressed in the SAPs and the endothelium of the AGM, respectively, where mib1 is detected. Indeed, Notch signaling was activated in the nascent HSCs at both sites. In the P-Sp explant culture, the overexpression of Dll1 in OP9 stromal cells rescued the failed production of hematopoietic progenitors in the Mib1^−/− P-Sp, while its activity was abolished by Mib1 knockdown. These results suggest that Mib1 is important for intraembryonic hematopoiesis not only in the aortic endothelium but also in the SAPs.     

Structure-activity relations of parasin I, a histone H2A-derived antimicrobial peptide

The structure-activity relations and mechanism of action of parasin I, a 19-amino acid histone H2A-derived antimicrobial peptide, were investigated. Parasin I formed an amphipathic alpha-helical structure (residues 9-17) flanked by two random coil regions (residues 1-8 and 18-19) in helix-promoting environments. Deletion of the lysine residue at the N-terminal [Pa(2-19)] resulted in loss of antimicrobial activity, but did not affect the alpha-helical content of the peptide. The antimicrobial activity was recovered when the lysine residue was substituted with another basic residue, arginine ([R(1)]Pa), but not with polar, neutral, or acidic residues. Progressive deletions from the C-terminal [Pa(1-17), Pa(1-15)] slightly increased the antimicrobial activity (1-4 microg/ml) without affecting the alpha-helical content of the peptide. However, further deletion [Pa(1-14)] resulted in nearly complete loss of antimicrobial activity and alpha-helical structure. Confocal microscopic analysis and membrane permeabilization assays showed that parasin I and its analogs with comparable antimicrobial activities localized to the cell membrane and subsequently permeabilized the outer and cytoplasmic membranes. Pa(1-14) also localized to the cell membrane, but lost membrane-permeabilizing activity, whereas Pa(2-19) showed poor membrane-binding and -permeabilizing activities. The results indicate that the basic residue at the N-terminal is essential for the membrane-binding activity of parasin I, and among the membrane-binding parasin I analogs, the alpha-helical structure is necessary for the membrane-permeabilizing activity.