• Volume 29, Issue 4

December 2004,   pages  367-526

• Clipboard: Benign anomaly to malign dysplasia: Variable expression of lamin B receptor mutations in humans

• Clipboard: Order in stress – Lessons from the inanimate world

• Clipboard: Eppin: A candidate male contraceptive vaccine?

• Commentary: F H C Crick (1916–2004)

• Commentary: The death of Francis Crick: the end of a golden age in biology

• Commentary: Critical fun with Francis Crick

• Physical aspect of microscopic behaviour of biomolecules

• Living in a physical world

The diversity of life on earth dazzles all of us – the rich profusion of its designs, the wide size range of its organisms, the complexities of its hierarchical levels, and so forth. Undaunted, we life scientists seek broadly applicable rules, common patterns of organizations, and order beneath the perceptual chaos; we look for alternatives to the easy answers of revealed truth.

Biology, no less than the physical sciences, treads this bumpy path – indeed the overt diversity of life puts especially bad bumps in its way. Perhaps its special difficulty underlies the gradual estrangement of biology from the more obviously successful physics of the post-Newtonian era and its awkward reintegration into the larger world of science in the twentieth century. That process remains incomplete; blame, if leveled, rests on the untidiness and distinctiveness of the subject. The tidy formulas of Newtonian physics work even less well for us than they do for, say, practicing engineers. Life directs its chemistry with sets of governing molecules and carries it out with the aid of catalysts of breathtaking specificity. And biology enjoys a strange organizing principle, evolution by natural selection, barely hinted at elsewhere in science.

No aspect of this reintegration has been (and continues to be) more successful than what we have come to call molecular biology – a statement at once fashionable and incontrovertible, one with which I have no grounds to take issue. What matters here, indeed the entire justification for the essays that begin with the one here, comes down to the following. The very success of this chemically-reductionist biology too easily diverts us from other conjunctions of physical science and biology.

This series will explore aspects of biology that reflect the physical world in which organisms find themselves. Evolution can do wonders, but it cannot escape its earthy context – a certain temperature range, a particular gravitational acceleration, the physical properties of air and water, and so forth. Nor can it tamper with mathematics. The baseline they provide both imposes constraints and affords opportunities. I mean to explore both.

And I will take what other biologists might find an unfamiliar approach – one, by the way, that I have found productive enough to recommend. Instead of asking about the physical science behind a specific biological system, I will consider aspects of the physical world and ask what organisms, any organisms, make of each, both how they might capitalize on them and be in some fashion limited by them. In effect, this will be a search for commonalities and patterns, the only unusual feature being the physical rather than biochemical or phylogenetic bases. If this approach to science were a dart game, I would be thrown out – for throwing darts at a wall first and only subsequently painting targets around the points of impact.

The series will concern itself mainly (but not exclusively) with organisms rather than ecosystems or organelles. It will follow the author’s bias and personal experience toward mechanical matters, doing less than equal justice to radiations and electrical phenomena. It will be speculative, opinionated, and idiosyncratic, aiming to stimulate thought and perhaps even investigation, to open doors rather than just describing them.

When I began to do science, over forty years ago, I wondered first whether and then where I would get ideas worth pursuing. Now, on the cusp of retirement, I wonder what I am going to do with my accumulated headand notebooks-full of questions. Maybe we need something like a patent expiration date – if one does nothing with a hypothesis for some number of years, it should somehow revert to the public domain. I am not an unequivocal advocate of a strict rule, inasmuch as I have, on occasion, resurrected one of my old ideas, applying some additional insight or new tool in my experimental armamentarium – or just responding to a renewed interest. Still, these essays should, if nothing else, provide an opportunity to air untested ideas with some hope that others might care to pursue them.

• Isolation and characterization of a new mannose-binding lectin gene from Taxus media

In this paper, we report the cloning and characterization of the first mannose-binding lectin gene from a gymnosperm plant species, Taxus media. The full-length cDNA of T. media agglutinin (TMA) consisted of 676 bp and contained a 432 bp open reading frame (ORF) encoding a 144 amino acid protein. Comparative analysis showed that TMA had high homology with many previously reported plant mannose-binding lectins and that tma encoded a precursor lectin with a 26-aa signal peptide. Molecular modelling revealed that TMA was a new mannose-binding lectin with three typical mannose-binding boxes like lectins from species of angiosperms. Tissue expression pattern analyses revealed that tma is expressed in a tissue-specific manner in leaves and stems, but not in fruits and roots. Phylogenetic tree analyses showed that TMA belonged to the structurally and evolutionarily closely related monocot mannose-binding lectin superfamily. This study provides useful information to understand the molecular evolution of plant lectins.

• Bioefficacy and mode-of-action of some limonoids of salannin group from Azadirachta indica A. Juss and their role in a multicomponent system against lepidopteran larvae

Biological activities of the salannin type of limonoids isolated from Azadirachta indica A. Juss were assessed using the gram pod borer Helicoverpa armigera (Hubner) and the tobacco armyworm Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). Inhibition of larval growth was concomitant with reduced feeding by neonate and third instar larvae. All three compounds exhibited strong antifeedant activity in a choice leaf disc bioassay with 2.0, 2.3 and 2.8 𝜇g/cm2 of 3-O-acetyl salannol, salannol and salannin, respectively deterring feeding by 50% in S. litura larvae. In nutritional assays, all three compounds reduced growth and consumption when fed to larvae without any effect on efficiency of conversion of ingested food (ECI), suggesting antifeedant activity alone. No toxicity was observed nor was there any significant affect on nutritional indices following topical application, further suggesting specific action as feeding deterrents. When relative growth rates were plotted against relative consumption rates, growth efficiency of the H. armigera fed diet containing 3-O-acetyl salannol, salannol or salannin did not differ from that of starved control larvae (used as calibration curve), further confirming the specific antifeedant action of salannin type of limonoids. Where the three compounds were co-administered, no enhancement in activity was observed. Non-azadirachtin limonoids having structural similarities and explicitly similar modes of action, like feeding deterrence in the present case, have no potentiating effect in any combination.

• Effects of hypervitaminosis of vitamin B3 on silkworm biology

A high-dose of vitamin B3 in silkworm diet interrupts larval feeding and normal growth. High mortality of larvae occurs during molting and they cannot complete this process normally. Also the larvae exhibit nicotinamide hypervitaminosis symptoms such as immobility, dyspepsia, darkening of the skin, inability to excrete normally, exerting brownish fluid from anus and swelling of rectal muscles. Maximum larval weights in 1, 2 and 3 g/l treatments were 2.9, 1.6 and 1.2 g respectively, while maximum larval weight in the control was 5.6 g. Larval stage compared to control had increased 18, 26 and 31 days respectively. The concentration increase of uric acid in haemolymph demonstrates the hyperuricemia, while other measured biochemical compounds show significant decrease; sodium and potassium did not change significantly.

• Maxillary palp glomeruli and ipsilateral projections in the antennal lobe of Drosophila melanogaster

The antennal lobe was examined by Golgi-silver impregnation to differentiate the glomeruli depending on the source and types of inputs. Thirty-five of the 43 ‘identified’ olfactory glomeruli were Golgi-silver impregnated in the present study. Seven glomeruli compared to three, reported previously, were found to be targets of maxillary palp chemosensory neurons. These include glomeruli VA3, VC2, VM5, VA7m/VA7l of the ventral antennal lobe and DC2, DC3, DM5 of the dorsal antennal lobe. The number of glomeruli receiving the maxillary palp sensory projections tallies with the number of Drosophila olfactory receptors (seven) reported to be expressed exclusively in the maxillary palp. Twenty-eight Golgi-impregnated glomeruli were found to receive input from the antennal nerve. The ratio of glomeruli serving the maxillary palp to those serving the antenna (∼ 1 : 5) matches with the ratio of Drosophila olfactory receptors expressed in these two olfactory organs respectively. In addition to glomerulus V, glomeruli VP1-3, VL1, VL2a/2p and VC3m/3l were found to receive ipsilateral projections. Thus, additional ipsilateral glomeruli have been identified.

This article assesses the traditional systems of accessing and using plant genetic resources as well as the benefit sharing and systems of sanctioning infringement in the context of biodiversity related activities in specific areas in the Northwest province of Cameroon. The article also addresses the type research and development activities using plant genetic resources and associated traditional knowledge in the context of Cameroon, the current laws regulating such activities and the extent to which these activities and laws affect and/or protect the customary biodiversity rights of rural communities. The article uses these assessments to suggest the context under which a sui generis legislation for the protection of the biodiversity rights of rural communities can be established in Cameroon.

• Stress biology – from molecules to populations and environment

• Plant resistance to cold stress: Mechanisms and environmental signals triggering frost hardening and dehardening

This introductory overview shows that cold, in particular frost, stresses a plant in manifold ways and that the plant’s response, being injurious or adaptive, must be considered a syndrome rather than a single reaction. In the course of the year perennial plants of the temperate climate zones undergo frost hardening in autumn and dehardening in spring. Using Scots pine (Pinus sylvestris L.) as a model plant the environmental signals inducing frost hardening and dehardening, respectively, were investigated. Over 2 years the changes in frost resistance of Scots pine needles were recorded together with the annual courses of day-length and ambient temperature. Both act as environmental signals for frost hardening and dehardening. Climate chamber experiments showed that short day-length as a signal triggering frost hardening could be replaced by irradiation with far red light, while red light inhibited hardening. The involvement of phytochrome as a signal receptor could be corroborated by respective night-break experiments. More rapid frost hardening than by short day or far red treatment was achieved by applying a short period (6 h) of mild frost which did not exceed the plant’s cold resistance. Both types of signals were independently effective but the rates of frost hardening were not additive. The maximal rate of hardening was – 0.93°C per day and frost tolerance of < – 72°C was achieved. For dehardening, temperature was an even more effective signal than day-length.

• Plant response strategies to stress and disturbance: the case of aquatic plants

The environmental factors controlling the establishment and development of plants in different ecosystems are of two types, stress and disturbance. The effects of stress or disturbance on aquatic systems are discussed in relation to the following questions:

Can we predict the state and rate of recolonization after a disturbance? What are the strategies of recolonization developed by plants? How high is the resilience of a disturbed system? Two theories, the intermediate disturbance hypothesis, and the patch dynamics concept proposed to predict the composition, structure and dynamics of plants due to physical-chemical factors, were tested on two scales, that of communities and that of species, within two alluvial floodplains (the Rhine and the Rhône systems in France).

With regard to the change of community on a larger scale (i.e. the whole network of the cut-off channels in the floodplain), large gradients of connection and disturbance induce high diversities within communities. Moreover, the highest flood disturbance induces a higher species richness and the occurrence of a particular species. The change in species is analysed using biological traits (morphological, reproductive or physiological). In the floodplain of the river Rhône, the response of plants corresponds well to theory, i.e. that habitats with an intermediate disturbance are richer than more or less disturbed habitats. So we can predict, through the biological traits, the functioning of a habitat. The last remaining question is that of the resilience of the system, which can be discussed in terms of species competition and the risk of biological invasion after an opening of habitat.

• Heat stress response in plants: a complex game with chaperones and more than twenty heat stress transcription factors

Compared to the overall multiplicity of more than 20 plant Hsfs, detailed analyses are mainly restricted to tomato and Arabidopsis and to three important representatives of the family (Hsfs A1, A2 and B1). The three Hsfs represent examples of striking functional diversification specialized for the three phases of the heat stress (hs) response (triggering, maintenance and recovery). This is best illustrated for the tomato Hsf system:

1. HsfA1a is the master regulator responsible for hs-induced gene expression including synthesis of HsfA2 and HsfB1. It is indispensible for the development of thermotolerance.
2. Although functionally equivalent to HsfA1a, HsfA2 is exclusively found after hs induction and represents the dominant Hsf, the working horse” of the hs response in plants subjected to repeated cycles of hs and recovery in a hot summer period. Tomato HsfA2 is tightly integrated into a network of interacting proteins (HsfA1a, Hsp17-CII, Hsp17-CI) influencing its activity and intracellular distribution.
3. Because of structural peculiarities, HsfB1 acts as coregulator enhancing the activity of HsfA1a and/or HsfA2. But in addition, it cooperates with yet to be identified other transcription factors in maintaining and/or restoring housekeeping gene expression.
• Habitat diversity and adaptation to environmental stress in encysted embryos of the crustacean Artemia

Encysted embryos (cysts) of the brine shrimp, Artemia, provide excellent opportunities for the study of biochemical and biophysical adaptation to extremes of environmental stress in animals. Among other virtues, this organism is found in a wide variety of hypersaline habitats, ranging from deserts, to tropics, to mountains. One adaptation implicated in the ecological success of Artemia is p26, a small heat shock protein that previous evidence indicates plays the role of a molecular chaperone in these embryos. We add to that evidence here. We summarize recently published work on thermal tolerance and stress protein levels in embryos from the San Francisco Bay (SFB) of California inoculated into experimental ponds in southern Vietnam where water temperatures are much higher. New results on the relative contents of three stress proteins (hsp70, artemin and p26) will be presented along with data on cysts of A. tibetiana collected from the high plateau of Tibet about 4.5 km above sea level. Unpublished results on the stress protein artemin are discussed briefly in the context of this paper, and its potential role as an RNA chaperone. Interestingly, we show that the substantial tolerance of A. franciscana embryos to ultraviolet (UV) light does not seem to result from intracellular biochemistry but, rather, from their surrounding thick shell, a biophysical adaptation of considerable importance since these embryos receive heavy doses of UV in nature.

• Ecologically relevant stress resistance: from microarrays and quantitative trait loci to candidate genes – A research plan and preliminary results using Drosophila as a model organism and climatic and genetic stress as model stresses

We aim at studying adaptation to genetic and environmental stress and its evolutionary implications at different levels of biological organization. Stress influences cellular processes, individual physiology, genetic variation at the population level, and the process of natural selection. To investigate these highly connected levels of stress effects, it is advisable – if not critical – to integrate approaches from ecology, evolution, physiology, molecular biology and genetics. To investigate the mechanisms of stress resistance, how resistance evolves, and what factors contribute to and constrain its evolution, we use the well-defined model systems of Drosophila species, representing both cosmopolitan species such as D. melanogaster with a known genome map, and more specialized and ecologically well described species such as the cactophilic D. buzzatii. Various climate-related stresses are used as model stresses including desiccation, starvation, cold and heat. Genetic stress or genetic load is modelled by studying the consequences of inbreeding, the accumulation of (slightly) deleterious mutations, hybridization or the loss of genetic variability. We present here a research plan and preliminary results combining various approaches: molecular techniques such as microarrays, quantitative trait loci (QTL) analyses, quantitative PCR, ELISA or Western blotting are combined with population studies of resistance to climatic and genetic stress in natural populations collected across climatic gradients as well as in selection lines maintained in the laboratory.

• Subject Index

• Author Index

• Acknowledgements

• # Journal of Biosciences

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