Functional variation among frugivorous birds: implications for rainforest seed dispersal in a fragmented subtropical landscape

Seed dispersal plays a critical role in rainforest regeneration patterns, hence loss of avian seed dispersers in fragmented landscapes may disrupt forest regeneration dynamics. To predict whether or not a plant will be dispersed in fragmented forests, it is necessary to have information about frugivorous bird distribution and dietary composition. However, specific dietary information for frugivorous birds is often limited. In such cases, information on the seed-crushing behaviour, gape width and relative dietary dominance by fruit may be used to describe functional groups of bird species with respect to their potential to disperse similar seeds. We used this information to assess differences in the seed dispersal potential of frugivorous bird assemblages in a fragmented rainforest landscape of southeast Queensland, Australia. The relative abundance of frugivorous birds was surveyed in extensive, remnant and regrowth rainforest sites (16 replicates of each). Large-gaped birds with mixed diets and medium-gaped birds with fruit-dominated diets were usually less abundant in remnants and regrowth than in continuous forest. Small-gaped birds with mixed diets and birds with fruit as a minor dietary component were most abundant in regrowth. We recorded a similar number of seed-crushing birds and large-gaped birds with fruit-dominated diets across site types. Bird species that may have the greatest potential to disperse a large volume and wide variety of plants, including large-seeded plants, tended to be less abundant outside of extensive forests, although one species, the figbird Sphecotheres viridis, was much more abundant in these areas. The results suggest that the dispersal of certain plant taxa would be limited in this fragmented landscape, although the potential for the dispersal of large-seeded plants may remain, despite the loss of several large-gaped disperser species.     

Long-term effects of experimental nitrogen additions on foliar litter decay and humus formation in forest ecosystems

Decomposition rates and N dynamics of foliar litter from 4 tree species were measured over a 72 month period on the Chronic Nitrogen Addition plots at the Harvard Forest, Petersham MA, beginning in November 1988. Plots received nitrogen additions of 0, 5 and 15 g N m^-2yr^-1 in two different stand types: red pine and mixed hardwood. Bags were collected in August and November of each year and litter analysed for mass remaining, nitrogen, cellulose and lignin content. Mass remaining was significantly greater for litter in nitrogen treated plots than in control plots after 48 months. Lignin content of litter was significantly higher with nitrogen treatments but there was little effect of treatment on cellulose content. N concentration was similar between treatments, but greater mass remaining in treated plots resulted in a higher total amount of N in humus produced in the high N plot. This mechanism could be a sink for up to 1.5 g N·m^-2yr^-1 of the 1.5 g N·m^-2yr^-1 added annually to the high N plots. Reduced decomposition rates in conjunction with increased lignin accumulation could impact global carbon sequestration as well.     

A RFLP linkage map of Sorghum bicolor (L.) Moench

A RFLP linkage map of sorghum composed principally of markers detected with sorghum low-copy-number nuclear DNA clones has been constructed. The map spans 1789 cMs and consists of 190 loci grouped into 14 linkage groups. The 10 largest linkage groups consist of from 10 to 24 markers and from 103 to 237 cMs, and the other 4 linkage groups consist of from 2 to 5 markers and from 7 to 62 cMs. The map was derived in Sorghum bicolor ssp. bicolor by analysis of a F₂ population composed of 50 plants derived from a cross of IS 3620C, a guinea line, and BTx 623, an agronomically important inbred line derived from a cross between a zera zera (a caudatum-like sorghum) and an established kafir line. The restriction fragment length polymorphism (RFLP) frequency detected in this population using polymerase chain reaction (PCR)-amplifiable low-copy-number sorghum clones and five restriction enzymes was 51%. A minimal estimate of the number of clones that detect duplicate sequences is 11 %. Null alleles occurred at 13% of the mapped RFLP loci.     

The internal pH of the forespore compartment of Bacillus megaterium decreases by about 1 pH unit during sporulation.

Previous work has shown that the internal pH of dormant spores of Bacillus species is more than 1 pH U below that of growing cells but rises to that of growing cells in the first minutes of spore germination. In the present work the internal pH of the whole Bacillus megaterium sporangium was measured by the distribution of the weak base methylamine and was found to decrease by approximately 0.4 during sporulation. By using fluorescence ratio image analysis with a fluorescein derivative, 2',7'-bis(2-carboxyethyl)-5 (and -6)-carboxyfluorescein (BCECF), whose fluorescence is pH sensitive, the internal pH of the mother cell was found to remain constant during sporulation at a value of 8.1, similar to that in the vegetative cell. Whereas the internal pH of the forespore was initially approximately 8.1, this value fell to approximately 7.0 approximately 90 min before synthesis of dipicolinic acid and well before accumulation of the depot of 3-phosphoglyceric acid. The pH in the forespore compartment was brought to that of the mother cell by suspending sporulating cells in a pH 8 potassium phosphate buffer plus the ionophore nigericin to clamp the internal pH of the cells to that of the external medium. We suggest that at a minimum, acidification of the forespore may regulate the activity of phosphoglycerate mutase, which is the enzyme known to be regulated to allow 3-phosphoglyceric acid accumulation during sporulation.     

Small, acid-soluble, spore proteins and their genes from two species of Sporosarcina

Small, acid-soluble proteins (SASP) of both the alpha/beta- and gamma-type were present in spores of Sporosarcina ureae and S. halophila, and three genes encoding alpha/beta-type SASP in these species have been cloned and sequenced. The amino acid sequences of the Sporosarcina alpha/beta-type SASP are extremely homologous to those of Bacillus SASP, further indicative of the close evolutionary relationship between these genera.     

Regional Assessment of N Saturation using Foliar and Root \varvec {\delta}^{\bf 15}{\bf N}

N saturation induced by atmospheric N deposition can have serious consequences for forest health in many regions. In order to evaluate whether foliar may be a robust, regional-scale measure of the onset of N saturation in forest ecosystems, we assembled a large dataset on atmospheric N deposition, foliar and root and N concentration, soil C:N, mineralization and nitrification. The dataset included sites in northeastern North America, Colorado, Alaska, southern Chile and Europe. Local drivers of N cycling (net nitrification and mineralization, and forest floor and soil C:N) were more closely coupled with foliar than the regional driver of N deposition. Foliar increased non-linearly with nitrification:mineralization ratio and decreased with forest floor C:N. Foliar was more strongly related to nitrification rates than was foliar N concentration, but concentration was more strongly correlated with N deposition. Root was more tightly coupled to forest floor properties than was foliar . We observed a pattern of decreasing foliar values across the following species: American beech>yellow birch>sugar maple. Other factors that affected foliar included species composition and climate. Relationships between foliar and soil variables were stronger when analyzed on a species by species basis than when many species were lumped. European sites showed distinct patterns of lower foliar , due to the importance of ammonium deposition in this region. Our results suggest that examining values of foliage may improve understanding of how forests respond to the cascading effects of N deposition.     

Development of mammalian production cell lines expressing CNTO736, a glucagon like peptide‐1‐MIMETIBODYTM: Factors that influence productivity and product quality

In an attempt to develop a high producing mammalian cell line expressing CNTO736, a Glucagon like peptide‐1‐antibody fusion protein (also known as a Glucagon like peptide‐1 MIMETIBODY^TM), we have noted that the N‐terminal GLP‐1 portion of the MIMETIBODY^TM was susceptible to proteolytic degradation during cell culture, which resulted in an inactive product. Therefore, a number of parameters that had an effect on productivity as well as product quality were examined. Results suggest that the choice of the host cell line had a significant effect on the overall product quality. Product expressed in mouse myeloma host cell lines had a lesser degree of proteolytic degradation and variability in O‐linked glycosylation as compared to that expressed in CHO host cell lines. The choice of a specific CHOK1SV derived clone also had an effect on the product quality. In general, molecules that exhibited minimal N‐terminal clipping had increased level of O‐linked glycosylation in the linker region, giving credence to the hypothesis that O‐linked glycosylation acts to protect against proteolytic degradation. Moreover, products with reduced potential for N‐terminal clipping had longer in vivo serum half‐life. These findings suggest that early monitoring of product quality should be an essential part of production cell line development and therefore, has been incorporated in our process of cell line development for this class of molecules. Biotechnol. Bioeng. 2009;103: 162–176. © 2008 Wiley Periodicals, Inc.     

Gene expression profiling of early intervertebral disc degeneration reveals a down-regulation of canonical Wnt signaling and caveolin-1 expression: implications for development of regenerative strategies

Introduction

Early degeneration of the intervertebral disc (IVD) involves a change in cellular differentiation from notochordal cells (NCs) in the nucleus pulposus (NP) to chondrocyte-like cells (CLCs). The purpose of this study was to investigate the gene expression profiles involved in this process using NP tissue from non-chondrodystrophic and chondrodystrophic dogs, a species with naturally occurring IVD degeneration.

Methods

Dual channel DNA microarrays were used to compare 1) healthy NP tissue containing only NCs (NC-rich), 2) NP tissue with a mixed population of NCs and CLCs (Mixed), and 3) NP tissue containing solely CLCs (CLC-rich) in both non-chondrodystrophic and chondrodystrophic dogs. Based on previous reports and the findings of the microarray analyses, canonical Wnt signaling was further evaluated using qPCR of relevant Wnt target genes. We hypothesized that caveolin-1, a regulator of Wnt signaling that showed significant changes in gene expression in the microarray analyses, played a significant role in early IVD degeneration. Caveolin-1 expression was investigated in IVD tissue sections and in cultured NCs. To investigate the significance of Caveolin-1 in IVD health and degeneration, the NP of 3-month-old Caveolin-1 knock-out mice was histopathologically evaluated and compared with the NP of wild-type mice of the same age.

Results

Early IVD degeneration involved significant changes in numerous pathways, including Wnt/β-catenin signaling. With regard to Wnt/β-catenin signaling, axin2 gene expression was significantly higher in chondrodystrophic dogs compared with non-chondrodystrophic dogs. IVD degeneration involved significant down-regulation of axin2 gene expression. IVD degeneration involved significant down-regulation in Caveolin-1 gene and protein expression. NCs showed abundant caveolin-1 expression in vivo and in vitro, whereas CLCs did not. The NP of wild-type mice was rich in viable NCs, whereas the NP of Caveolin-1 knock-out mice contained chondroid-like matrix with mainly apoptotic, small, rounded cells.

Conclusions

Early IVD degeneration involves down-regulation of canonical Wnt signaling and Caveolin-1 expression, which appears to be essential to the physiology and preservation of NCs. Therefore, Caveolin-1 may be regarded an exciting target for developing strategies for IVD regeneration.