MtPM25 is an atypical hydrophobic late embryogenesis‐abundant protein that dissociates cold and desiccation‐aggregated proteins

Late embryogenesis‐abundant (LEA) proteins are one of the components involved in desiccation tolerance (DT) by maintaining cellular structures in the dry state. Among them, MtPM25, a member of the group 5 is specifically associated with DT in Medicago truncatula seeds. Its function is unknown and its classification as a LEA protein remains elusive. Here, evidence is provided that MtPM25 is a hydrophobic, intrinsically disordered protein that shares the characteristics of canonical LEA proteins. Screening protective activities by testing various substrates against freezing, heating and drying indicates that MtPM25 is unable to protect membranes but able to prevent aggregation of proteins during stress. Prevention of aggregation was also found for the water soluble proteome of desiccation‐sensitive radicles. This inhibition was significantly higher than that of MtEM6, one of the most hydrophilic LEA protein associated with DT. Moreover, when added after the stress treatment, MtPM25 is able to rapidly dissolve aggregates in a non‐specific manner. Sorption isotherms show that when it is unstructured, MtPM25 absorbs up to threefold more water than MtEM6. MtPM25 is likely to act as a protective molecule during drying and plays an additional role as a repair mechanism compared with other LEA proteins.     

Which proximate factor determines sexual size dimorphism in tiger snakes?

Diverse interactions between factors that influence body size complicate the identification of the primary determinants of sexual size dimorphism. Using data from a long‐term field study (1997–2009), we examined the contributions of the main proximate factors potentially influencing sexual size dimorphism from birth to adulthood in tiger snakes (Notechis scutatus). Data on body size, body mass and body condition of neonates, juveniles and adults were obtained by mark–recapture. Frequent recaptures allowed us to monitor reproductive status, diet and food intake, and to estimate survival and growth rates in age and sex classes. Additional data from females held briefly in captivity enabled us to assess reproductive output and the body mass lost at parturition (proxies for reproductive effort). From birth to maturity, individuals of both sexes experienced similar growth and mortality rates. We found no difference in diet, feeding and survival rates between the sexes, nor between juveniles and adults. On maturity, despite comparable diet and food intake by both sexes, the high energy requirements of vitellogenesis and gestation were responsible for a depletion of body reserves and probably resulted in a marked decrease in growth rates. Males were largely exempt from such costs of reproduction, and so could grow faster than females and attain larger body sizes. The absence of niche divergence between the sexes (uniformity of habitat, lack of predators) suggests that the impact of differential energetic investment for reproduction on growth rate is probably the main proximate factor influencing sexual size dimorphism in this species. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 668–680.     

The skull of Microtia, an extinct burrowing murine rodent of the late Neogene Gargano palaeoisland

The Neogene Gargano paleoisland (southern Italy) has yielded numerous fossil vertebrates, some of them showing extraordinary morphological peculiarities. Among these endemic species, the rodent genus Microtia Freudenthal, 1976, is represented by three main lineages that evolve toward gigantism. This genus is the most significant and abundant rodent represented in the Gargano palaeofaunas. Its evolutionary trends reveal an increase of size, accompanied by a complication of molar structure. Before carrying out a study on the Gargano rodent community, its structure and its evolution, it was necessary to characterize Microtia's ecological adaptations. Microtia was adapted to burrowing life, which appears to be a unique adaptation for a murine rodent, since European burrowing Plio-Pleistocene and extant rodents are only represented by arvicolids. Therefore, the extinction of Microtia is likely to be due to competition with arvicolids after the breakdown of isolation, since they occupied very similar ecological niches.     

The detection of Glomus spp. (arbuscular mycorrhizal fungi) forming mycorrhizas in three plants, at different stages of seedling development, using mycorrhiza-specific isozymes

A series of glasshouse experiments was used to determine mycorrhiza-specific isozymes (MSIs) produced by five species of Glomus colonizing roots of a desert shrub legume ( Anthyllis cytisoides L.), Thymus vulgaris L. and Allium porrum L. over time. Extracts of colonized roots were electrophoresed on non-denaturing polyacrylamide gels (PAGE) and stained for 10 different enzymes. Staining protocols for esterase, glutamate oxaloacetate transaminase, alkaline phosphatase and malate dehydrogenase provided MSIs for the mycorrhizas formed by different arbuscular mycorrhizal (AM) fungi that had colonized roots of the three host plants. There was no apparent correlation between levels of colonization or arbuscular intensities, at or between each sampling, and the presence of MSIs. The development of colonization by the AM fungi differed little between the three plants when assessed with two methods of estimating fungal biomass. The variety of MSIs detected might reflect the diversity of metabolic activities of these Glomus species and, possibly, differing ecological functions. The high-level induction of two alkaline phosphatase MSIs in the mycorrhizas of Anthyllis cytisoides colonized by Glomus microaggregatum BEG56 was used to track the fate of this fungus when the same plant was inoculated and transplanted into a semi-arid site in south-east Spain. The probable fungal origin of the isozyme was indicated by detection of the same isozyme in the extraradical mycelium formed by Glomus microaggregatum BEG56 on Allium porrum . The use of MSIs to detect the mycorrhizas of species of Glomus in colonized roots is discussed.     

Inter‐individual variation in movement: is there a mobility syndrome in the large white butterfly Pieris brassicae?

1. One of the main drivers of the genesis and maintenance of biodiversity is mobility, i.e. the net result of the interaction between physiological performances (movement capacity) and behavioural decisions (movement decisions). Although several previous studies have found personality traits related to mobility, it is not yet clear whether mobility involves a real syndrome, i.e. whether individuals showing good movement capacity are also more likely to decide to move, and whether these inter‐individual differences are consistent across time. 2. The aim of the present study was therefore to disentangle the mechanisms underlying the maintenance of inter‐individual variation in mobility by measuring three traits related to mobility under experimental conditions in a butterfly species, and to test the existence of correlations between these traits. These measures implied movement capacity and movement decision. 3. It was shown that mobility‐related traits were (i) consistent across time, (ii) inter‐correlated, and (iii) dependent upon sex and morphology. 4. These results therefore suggest the existence of a mobility syndrome in a butterfly. Such findings highlight the necessity to accurately integrate inter‐individual variation (behavioural syndrome) in our comprehension of the evolution of movement strategies.