Population trends for humpback whales (Megaptera novaeangliae) foraging in the Francisco Coloane Coastal‐Marine Protected Area,Magellan Strait,Chile

In 2003 a feeding aggregation of southeastern Pacific humpback whales (Megaptera novaeangliae) was reported in the Magellan Strait. While Chile established its first marine national park in the Strait to protect humpback whale habitat, fatal ship strikes remain a concern because of overlap with a busy shipping lane. To better understand population risk, we estimated abundance and survival for this population using Bayesian robust‐design mark‐recapture models fit to photographic data from 2004 to 2016. Overall, the model estimated a total of 204 whales (95% CI: 199–210) during the last 12 yr, and 93 (95% CI: 86–100) in the 2016/2017 austral summer. The population grew at 2.3% (CI: 2.1%–3.1%), an annual increase of two whales. Annual survival (including calves) was estimated at 0.892 (CI: 0.871–0.910). Our results corroborate a persistent feeding population, but one that is increasing relatively slowly. Owing to its vulnerability stemming from its small size, coupled with significant overlap with a busy shipping lane, we argue this subpopulation is at significant risk from ship strikes and may be one of the few populations where anthropogenic mortalities could regulate population dynamics. We therefore encourage continued monitoring via photographic mark‐resighting surveys, and analyses explicitly investigating potential population‐level ship strike effects.     

Mutations in the Pseudomonas syringae avrRpt2 gene that dissociate its virulence and avirulence activities lead to decreased efficiency in AvrRpt2-induced disappearance of RIN4

The avrRpt2 gene from Pseudomonas syringae pv. tomato exhibits avirulence activity on Arabidopsis expressing the resistance gene RPS2 but promotes bacterial virulence on susceptible rps2 Arabidopsis. To understand the functional relationship between the avirulence and virulence activities of avrRpt2, we analyzed a series of six avrRpt2 mutants deficient in eliciting the RPS2-dependent hypersensitive response. We show that the mutants are also severely impaired in triggering RSP2-dependent resistance. Four of these mutants are severely impaired in their virulence activity, whereas two alleles, encoding C-terminal deletions of AvrRpt2, retain significant but slightly reduced virulence activity. Thus, the avirulence and virulence activities of avrRpt2 can be genetically uncoupled. We tested the ability of the two C-terminal deletion mutants to trigger AvrRpt2-induced elimination of the Arabidopsis RIN4 protein and show that they retain this activity but are less efficient than wild-type AvrRpt2. Thus, reduced AvrRpt2 virulence activity is correlated with reduced efficiency in the induction of RIN4 disappearance. This suggests that an alteration in kinetics of RIN4 disappearance triggered by the C-terminal deletion mutants may provide the mechanistic basis for the uncoupling of the avirulence and virulence activities of avrRpt2.     

The Pseudomonas syringae type III effector AvrRpt2 promotes virulence independently of RIN4, a predicted virulence target in Arabidopsis thaliana

AvrRpt2, an effector protein from Pseudomonas syringae pv. tomato (Pst), behaves as an avirulence factor that activates resistance in Arabidopsis thaliana lines expressing the resistance gene RPS2. AvrRpt2 can also enhance pathogen fitness by promoting the ability of the bacteria to grow and to cause disease on susceptible lines of A. thaliana that lack functional RPS2. The activation of RPS2 is coupled to the AvrRpt2-induced disappearance of the A. thaliana RIN4 protein. However, the significance of this RIN4 elimination to AvrRpt2 virulence function is unresolved. To clarify our understanding of the contribution of RIN4 disappearance to AvrRpt2 virulence function, we generated new avrRpt2 alleles by random mutagenesis. We show that the ability of six novel AvrRpt2 mutants to induce RIN4 disappearance correlated well with their avirulence activities but not with their virulence activities. Moreover, the virulence activity of wild-type AvrRpt2 was detectable in an A. thaliana line lacking RIN4. Collectively, these results indicate that the virulence activity of AvrRpt2 in A. thaliana is likely to rely on the modification of host susceptibility factors other than, or in addition to, RIN4.     

Factors associated with the catastrophic decline of a cloudforest frog fauna in Guatemala

Comparison of recent and historical surveys of frog populations in cloudforest habitat in Sierra de las Minas, Guatemala, indicated population declines and local extirpation of several species. Pathological exams of diseased tadpoles indicated infection by amphibian chytridiomycosis. The local habitat has been severely altered by recent establishment of large-scale leatherleaf fern production. Analysis of water chemistry at our study site suggested increased nitrogenation associated with the leatherleaf industry.     

The role of two isoenzymes of alpha-amylase of Araucaria araucana (Araucariaceae) on the digestion of starch granules during germination

Starch is the principal reserve of Araucaria araucana seeds, and it is hydrolysed during germination mainly by alpha-amylase. There are several alpha-amylase isoenzymes whose patterns change in the embryo and in the megagametophyte from the one observed in quiescent seeds (T(0)) to a different one observed 90 h after imbibition (T(90)). The objective of this research was to study the roles of two purified alpha-amylase isoenzymes by in vitro digestion of starch granules extracted from the tissues at two times of imbibition: one is abundant in quiescent seeds and the other is abundant after 90 h of imbibition. The isoenzymes digested the starch granules of their own stage of germination better, since the isoenzyme T(0) digested starch granules mainly from quiescent seeds, while the isoenzyme T(90) digested starch mainly at 90 h of imbibition. The sizes of the starch granule and the tissue from which these granules originated make a difference to digestion by the isoenzymes. Embryonic isoenzyme T(0) digested large embryonic starch granules better than small and medium-sized granules, and better than those isolated from megagametophytes. Similarly isoenzyme T(90) digested small embryonic starch granules better than medium-sized and large granules, and better than those isolated from megagametophytes. However, a mixture of partially purified megagametophytic isoenzymes T(0) and T(90) digested the megagametophytic granules better than those isolated from embryos. Studies of in vitro sequential digestion of starch granules with these isoenzymes corroborated their specificity. The isoenzyme T(90) digested starch granules previously digested by the isoenzyme T(0). This suggests that in vivo these two isoenzymes may act sequentially in starch granule digestion.     

Genetics of P-element transposition into Drosophila melanogaster centric heterochromatin

Heterochromatin is a major component of higher eukaryotic genomes, but progress in understanding the molecular structure and composition of heterochromatin has lagged behind the production of relatively complete euchromatic genome sequences. The introduction of single-copy molecular-genetic entry points can greatly facilitate structure and sequence analysis of heterochromatic regions that are rich in repeated DNA. In this study, we report the isolation of 502 new P-element insertions into Drosophila melanogaster centric heterochromatin, generated in nine different genetic screens that relied on mosaic silencing (position-effect variegation, or PEV) of the yellow gene present in the transposon. The highest frequencies of recovery of variegating insertions were observed when centric insertions were used as the source for mobilization. We propose that the increased recovery of variegating insertions from heterochromatic starting sites may result from the physical proximity of different heterochromatic regions in germline nuclei or from the association of mobilizing elements with heterochromatin proteins. High frequencies of variegating insertions were also recovered when a potent suppressor of PEV (an extra Y chromosome) was present in both the mobilization and selection generations, presumably due to the effects of chromatin structure on P-element mobilization, insertion, and phenotypic selection. Finally, fewer variegating insertions were recovered after mobilization in females, in comparison to males, which may reflect differences in heterochromatin structure in the female and male germlines. FISH localization of a subset of the insertions confirmed that 98% of the variegating lines contain heterochromatic insertions and that these schemes produce a broader distribution of insertion sites. The results of these schemes have identified the most efficient methods for generating centric heterochromatin P insertions. In addition, the large collection of insertions produced by these screens provides molecular-genetic entry points for mapping, sequencing, and functional analysis of Drosophila heterochromatin.     

Behaviour of ribosomal genes and nucleolar domains during activation in sugarcane (Saccharum officinarum L.) root primordia: from the unsoaked quiescent state to the steady state of proliferation

Changes in the organisation of ribosomal genes and nucleolar protein components were analysed in sugarcane (Saccharum officinarum L. cv Cristalina) from the time the quiescent primordia of the radical bands of nodes were stimulated to proliferate by water imbibition, until the meristematic population reached the steady state of proliferation in the growing roots. The kinetics of proliferation was evaluated by flow cytometry, and by the mitotic indexes, in roots of different lengths. All the quiescent cells were in a pre-replicative state (G0), with a 2C DNA content. During their activation process, they progressively reached the steady state of proliferation (mitotic index 7%), with rather fixed frequencies for cells with 2C (G1), 4C (G2), and values between them corresponding to cells replicating their DNA. Decondensation of the ribosomal genes was followed by FISH with probes for the major 25S and 18S rRNAs, and variations in the numbers of nucleoli were recorded in squashed cells after silver staining. The ultrastructure of nucleoli was analysed by electron microscopy, using the EDTA regressive staining for ribonucleoproteins. Quiescent nucleoli showed a clear segregation of their main components: Fibrillar Centre, Dense Fibrillar Component and Cajal's bodies while lacked any Granular Component. However the proliferating ones showed them highly intermingled, except for the Cajal's bodies. Our results revealed a high plasticity of the nucleolar domains in response to cell activation, and allowed to establish a correlation between dispersion of NORs with formation of small fibrillar centers and a nucleolus with all its domains intermingled, and the activation of cell proliferation during root sprouting.     

In vivo delivery of the caveolin-1 scaffolding domain inhibits nitric oxide synthesis and reduces inflammation

Caveolin-1, the primary coat protein of caveolae, has been implicated as a regulator of signal transduction through binding of its "scaffolding domain" to key signaling molecules. However, the physiological importance of caveolin-1 in regulating signaling has been difficult to distinguish from its traditional functions in caveolae assembly, transcytosis, and cholesterol transport. To directly address the importance of the caveolin scaffolding domain in vivo, we generated a chimeric peptide with a cellular internalization sequence fused to the caveolin-1 scaffolding domain (amino acids 82-101). The chimeric peptide was efficiently taken up into blood vessels and endothelial cells, resulting in selective inhibition of acetylcholine (Ach)-induced vasodilation and nitric oxide (NO) production, respectively. More importantly, systemic administration of the peptide to mice suppressed acute inflammation and vascular leak to the same extent as a glucocorticoid or an endothelial nitric oxide synthase (eNOS) inhibitor. These data imply that the caveolin-1 scaffolding domain can selectively regulate signal transduction to eNOS in endothelial cells and that small-molecule mimicry of this domain may provide a new therapeutic approach.