ROLE OF PSEUDOBULBS IN GROWTH AND FLOWERING OF CATASETUM VIRIDIFLAVUM (ORCHIDACEAE)

In Catasetum viridiflavum Hook., a drought-deciduous orchid from central Panama that produces unisexual flowers, plants possess up to nine annually-produced pseudobulbs. I investigated the role of these structures in plant growth and flowering by 1) relating annual shoot size and flower production to the size and number of pseudobulbs possessed by plants, 2) experimentally severing connections between young and old pseudobulbs when plants were dormant and monitoring their subsequent vegetative growth and flowering, and 3) determining the seasonal variation in water content, total nonstructural carbohydrates, nitrogen, and phosphorus in pseudobulbs. In small plants (1 to 3 pseudobulbs) pseudobulb stores appeared important to both vegetative growth and flowering. In larger (= older) plants, pseudobulb number was not related to vegetative growth and experimental separations of young from old pseudobulbs did not affect growth. However, flower production by experimental plants was significantly reduced relative to controls. Male plants were usually smaller than female plants in the areas studied; however, experimental reductions of pseudobulb number did not affect the sex expression of plants. All measured nutritional components of pseudobulbs exhibited significant seasonal variation. Carbohydrates appeared most important for supporting growth immediately following dormancy. Nitrogen and phosphorus were less important for this role and may have been more important for determining the number of flowers produced by plants.     

Spectral sensitivity and photopigments of a nocturnal prosimian,the bushbaby (Otolemur crassicaudatus)

Earlier studies yielded conflicting conclusions on the types of photoreceptors and photopigments found in the eyes of nocturnal prosimians. In this investigation a noninvasive electrophysiological procedure, electroretinogram flicker photometry, was employed to measure scotopic and photopic spectral sensitivity in the thick-tailed bushbaby (Otolemur crassicaudatus). The scotopic spectral sensitivity function of the bushbaby has a peak of about 507 nm. Under photopic test conditions, spectral sensitivity shifts toward the longer wavelengths. The results from a series of adaptation experiments indicate that the cones of the bushbaby retina contain only a single type of cone photopigment (peak sensitivity at about 545 nm). One implication from this result is that these animals do not have color vision. The photopigment arrangement of the bushbaby is different from that earlier found in diurnal and crepuscular prosimians but is similar to that of the owl monkey, the only nocturnal simian. © 1996 Wiley-Liss, Inc.     

Reporter-linked monitoring of transgene expression in living cells using the ecdysone-inducible promoter system

Inducible promoter systems such as the ecdysone-inducible system or the tetracycline-regulated expression systems have proven to be powerful tools in studying gene function. In practice, such systems have met with the difficulty that either the vector expressing the transactivator gene or the vector carrying the response element are frequently silenced by flanking genomic sequences after stable integration. In order to identify those cells in a heterogeneous population in which a transgene is expressed from an ecdysone-inducible promoter, we have created the vector p2ER-EGFP/mcs that contains two ecdysone-inducible expression cassettes in tandem. Using two reporter genes, lacZ and green fluorescent protein (EGFP), we demonstrate that the expression of both genes can be co-induced from a very low baseline in CHO cells expressing the modified ecdysone receptor and the retinoid X receptor. The expression of EGFP and lacZ from vector p2ER-EGFP/lacZ follows the same Muristerone A concentration-dependence as that of EGFP from vector pER-EGFP, indicating that the juxtaposition of the two inducible promoters in vector p2ER-EGFP/mcs does not cause cross interference between them. We suggest that this modification of the ecdysone-inducible promoter system will allow for the visual control of the induced expression of other genes by Muristerone A.     

Brain mechanisms for extracting spatial information from smell

Forty years ago, von Békésy demonstrated that the spatial source of an odorant is determined by comparing input across nostrils, but it is unknown how this comparison is effected in the brain. To address this, we delivered odorants to the left or right of the nose, and contrasted olfactory left versus right localization with olfactory identification during brain imaging. We found nostril-specific responses in primary olfactory cortex that were predictive of the accuracy of left versus right localization, thus providing a neural substrate for the behavior described by von Békésy. Additionally, left versus right localization preferentially engaged a portion of the superior temporal gyrus previously implicated in visual and auditory localization, suggesting that localization information extracted from smell was then processed in a convergent brain system for spatial representation of multisensory inputs.     

Barriers to Forest Regeneration in an Abandoned Pasture in Puerto Rico

Sources of forest regeneration (soil seed bank, seed rain) and barriers to seedling establishment were examined in a recently abandoned pasture in eastern Puerto Rico. Few woody species were found in the soil seed bank or in the seed rain. The number of seeds and species in the seed rain and soil seed bank declined with distance from the adjacent secondary forest. Nine species naturally dispersed and colonized plots during the study, with the wind‐dispersed tree Tabebuia heterophylla being the predominant colonizer (91% of all seedlings). Barriers to seedling establishment were determined using a blocked field experiment with eleven woody species representative of a variety of life histories. Each species was planted under the pasture vegetation (control) or in areas where all vegetation was removed (removal). Germination was enhanced for four species in the control treatment, five species were not affected, and two species did not germinate under either treatment. Survival to 6 months was higher in the removal treatment for two species. Seedling biomass was greater in the removal treatment at 12 months for one species. Seed mass was a good predictor of germination success and final shoot biomass, but not survival. This study demonstrates that seeding recently abandoned pastures with a mix of known pioneer species may accelerate the rate of secondary succession, but some species will have to be planted in later successional stages in order to overcome strong barriers to establishment.     

Use of PIT tags to assess individual heterogeneity of laboratory‐reared juveniles of the endangered Cumberlandian combshell (Epioblasma brevidens) in a mark–recapture study

The federally endangered Cumberlandian combshell (Epioblasma brevidens) was propagated and reared to taggable size (5–10 mm), and released to the Powell River, Tennessee, to augment a relict population. Methodology using passive integrated transponder (PIT) tags on these mussels greatly facilitated the detection process. The overall mean detection probability and survival rate of released individuals reached 97.8 to 98.4% and 99.7 to 99.9% (per month), respectively, during nine successive recapture occasions in the 2‐year study period, regardless of seasonality. Nonhierarchical models and hierarchical models incorporating individual and seasonal variations through a Bayesian approach were compared and resulted in similar performance of prediction for detection probability and survival rate of mussels. This is the first study to apply the mark–recapture method to laboratory‐reared mussels using PIT tags and stochastic models. Quantitative analyses for individual heterogeneity allowed examination of demographic variance and effects of heterogeneity on population dynamics, although the individual and seasonal variations were small in this study. Our results provide useful information in implementing conservation strategies of this faunal group and a framework for other species or similar studies.     

AFAP1 Is a Novel Downstream Mediator of TGF-β1 for CCN2 Induction in Osteoblasts

Background

CCN2 acts as an anabolic growth factor to regulate osteoblast differentiation and function. CCN2 is induced by TGF-β1 and acts as a mediator of TGF-β1 induced matrix production in osteoblasts and Src is required for CCN2 induction by TGF-β1; however, the molecular mechanisms that control CCN2 induction in osteoblasts are poorly understood. AFAP1 binds activated forms of Src and can direct the activation of Src in certain cell types, however a role for AFAP1 downstream of TGF-β1 or in osteoblats is undefined. In this study, we investigated the role of AFAP1 for CCN2 induction by TGF-β1 in primary osteoblasts.

Results

We demonstrated that AFAP1 expression in osteoblasts occurs in a biphasic pattern with maximal expression levels occurring during osteoblast proliferation (~day 3), reduced expression during matrix production/maturation (~day 14–21), an a further increase in expression during mineralization (~day 21). AFAP1 expression is induced by TGF-β1 treatment in osteoblasts during days 7, 14 and 21. In osteoblasts, AFAP1 binds to Src and is required for Src activation by TGF-β1 and CCN2 promoter activity and protein induction by TGF-β1 treatment was impaired using AFAP1 siRNA, indicating the requirement of AFAP1 for CCN2 induction by TGF-β1. We also demonstrated that TGF-β1 induction of extracellular matrix protein collagen XIIa occurs in an AFAP1 dependent fashion.

Conclusions

This study demonstrates that AFAP1 is an essential downstream signaling component of TGF-β1 for Src activation, CCN2 induction and collagen XIIa in osteoblasts.     

Immediate response of fish communities and water chemistry to causeway breaching and bridge installation in the Kaouk River estuary,British Columbia,Canada

The Kaouk River estuary is located on the northwest coast of Vancouver Island, British Columbia, Canada, in the Treaty Settlement Lands of the Ka:'yu:'k't'h'/Che:k'tles7et'h First Nations. Stretching across the widest point of this estuary is a causeway providing road access to Fair Harbour. This causeway was observed to decrease habitat connectivity throughout the estuary, specifically limiting juvenile salmon access to high‐quality rearing habitat in the tidal marsh. As such, the causeway was breached in 2019 and a bridge was installed. Juvenile salmon were observed using the new connection and were captured both up and downstream of the causeway immediately following breaching. Postbreach water chemistry (dissolved oxygen, pH, salinity, and temperature) near the causeway was recorded within the range of values observed throughout the estuary. Use of the breach by juvenile salmon and homogenized water chemistry indicate the project succeeded in improving habitat connectivity within the Kaouk River estuary and has enhanced juvenile salmon access to 2.7 km² of wetland rearing habitat.     

Meta‐analysis of global livestock urine‐derived nitrous oxide emissions from agricultural soils

Nitrous oxide (N₂O) is an air pollutant of major environmental concern, with agriculture representing 60% of anthropogenic global N₂O emissions. Much of the N₂O emissions from livestock production systems result from transformation of N deposited to soil within animal excreta. There exists a substantial body of literature on urine patch N₂O dynamics, we aimed to identify key controlling factors influencing N₂O emissions and to aid understanding of knowledge gaps to improve GHG reporting and prioritize future research. We conducted an extensive literature review and random effect meta‐analysis (using REML) of results to identify key relationships between multiple potential independent factors and global N₂O emissions factors (EFs) from urine patches. Mean air temperature, soil pH and ruminant animal species (sheep or cow) were significant factors influencing the EFs reviewed. However, several factors that are known to influence N₂O emissions, such as animal diet and urine composition, could not be considered due to the lack of reported data. The review highlighted a widespread tendency for inadequate metadata and uncertainty reporting in the published studies, as well as the limited geographical extent of investigations, which are more often conducted in temperate regions thus far. Therefore, here we give recommendations for factors that are likely to affect the EFs and should be included in all future studies, these include the following: soil pH and texture; experimental set‐up; direct measurement of soil moisture and temperature during the study period; amount and composition of urine applied; animal type and diet; N₂O emissions with a measure of uncertainty; data from a control with zero‐N application and meteorological data.