Evolving proteins at Darwin's bicentenary

A report of the Biochemical Society/Wellcome Trust meeting 'Protein Evolution - Sequences, Structures and Systems', Hinxton, UK, 26-27 January 2009.     

Sex allocation in an hermaphroditic plant: the case of gynodioecy in Thymus vulgaris L.

Resource allocation to male and female functions was investigated in Thymus vulgaris L. (thyme), a gynodioecious species, in which females produce twice as many seeds as hermaphrodites. Negative correlations were found between male and female fertility of hermaphrodites, providing evidence of a trade-off. There was a high variability in sexual investment, some of the hermaphrodites functioning almost as males, and others almost as females. Estimation of the relative cost of male and female gametes showed that the female advantage in seed production was mainly due to reallocation of the resources not allocated to male function into female function. The determination of sex allocation was shown to have a genetic component, and there were some evidence that an interaction between nuclear and cytoplasmic genomes was involved.     

Links between morphology and function of the pollen wall: an experimental approach

The wall of pollen grains exhibits morphological variation in many features including apertures, ornamentation and thickness, but the function of these characters remains to be clarified. It has been suggested that they are involved in the accommodation of volume changes (harmomegathy). To investigate this further, we developed a protocol that induces a controlled hydration of the pollen without affecting its metabolism and we applied it to six species differing in their pollen wall morphology. The entry of water caused pollen swelling and volume increase leading to breakage of the wall and/or of the plasma membrane, such that the per cent of intact grains was negatively correlated with the level of hydration. Qualitative and quantitative differences were observed between the species. Breakage of the exine was observed only in pollen lacking apertures and with thin exine. Variation in the exine ornamentation and thickness could explain the interspecific differences observed for the rates of breakage of the plasma membrane. Our results suggest that pollen wall morphology matters for survival and maintenance of pollen integrity further to volume increase due to hydration. We propose a rationale for future studies that should allow disentangling the contribution of different pollen morphological and physiological features to harmomegathy.     

THE IDENTITY OF THE SWEDE MIDGE, WITH NOTES ON ITS BIOLOGY

A brief historical summary is given of the literature concerning Contarinia nasturtii Kieffer, C. torquens de Meijere and C. geisenheyneri Riibsaamen, three gall midges (Cecidomyidae) which have been associated respectively with leaf damage on Brassica spp. in England, identical malformation on the Continent and swollen and closed flowers of Brassica spp. in Europe.
Following the discovery in England of the true Contarinia nasturtii causing swollen and closed flowers oiRorippa amphibia, preliminary experiments have shown that midges from this source will also cause similar damage to swede flowers and that they are the same species as those attacking R. amphibia blossom in the Netherlands.
Further preliminary experiments have shown that swede midge derived from rape leaf axils will also cause identical damage to radish flowers in addition to breeding successfully on the leaves of turnip, swede, cabbage and radish.
Male midges derived from Rorippa blossom have been mated with females from rape leaf axils, and their offspring have been reared on Rorippa flowers and on turnip leaves.
This biological evidence confirms the previous supposition based on morphological grounds that the swede midge is Contarinia nasturtii Kieffer and will cause either flower or leaf damage. Consequently, C. torquens de Meijere and C. geisenheyneri Riibsaamen must remain synonyms.
The shortest time for a generation (from parent to first offspring midge) to develop was 24–39 days in an unheated open glasshouse during June-July in 1949 at Harpenden. Under the same conditions, the shortest time for the next generation from late July to August was 29–32 days. C. nasturtii is the first Contarinia species in which unisexual families have been discovered.     

The Epidemiology of Dental Diseases in the Elderly1

This paper summarizes and evaluates epidemiologic evidence on adult dental conditions with a focus on older adults. Information is presented on coronal caries; root caries; loss of teeth, attrition, abrasion, and erosion; periodontal diseases; and oral cancer. The author concludes that the oral health status of the elderly in the United States is essentially unknown. There are no recent, representative population base studies of oral conditions in the elderly. Studies of prevalence or incidence of oral diseases typically include few elderly persons or describe a select group of elderly who are at high risk. Furthermore, it is not really known whether the incidence and prevalence of coronal caries or root caries is actually increasing or is part of a cohort effect. While oral cancers have been shown to increase with age, there is no information as to whether their incidence rates are increasing. While, clinically, there are indications that attrition, abrasion and erosion are characteristics that are more likely to be seen in older adults, there is no information about their distribution in the population. There is evidence that loss of teeth is decreasing but nothing is known about the patterning of that loss. As for periodontal diseases, much work is needed to identify various syndromes that may be distinguished by their distribution in the population as well as determining whether periodontitis is a condition responsible for a majority of tooth loss or just the majority of tooth loss in a small high risk group. In addition, some suggestions are presented for future directions of research in this area.