Association mapping for chilling tolerance in elite flint and dent maize inbred lines evaluated in growth chamber and field experiments

Chilling sensitivity of maize is a strong limitation for its cultivation in the cooler areas of the northern and southern hemisphere because reduced growth in early stages impairs on later biomass accumulation. Efficient breeding for chilling tolerance is hampered by both the complex physiological response of maize to chilling temperatures and the difficulty to accurately measure chilling tolerance in the field under fluctuating climatic conditions. For this research, we used genome‐wide association (GWA) mapping to identify genes underlying chilling tolerance under both controlled and field conditions in a broad germplasm collection of 375 maize inbred lines genotyped with 56 110 single nucleotide polymorphism (SNP). We identified 19 highly significant association signals explaining between 5.7 and 52.5% of the phenotypic variance observed for early growth and chlorophyll fluorescence parameters. The allelic effect of several SNPs identified for early growth was associated with temperature and incident radiation. Candidate genes involved in ethylene signalling, brassinolide, and lignin biosynthesis were found in their vicinity. The frequent involvement of candidate genes into signalling or gene expression regulation underlines the complex response of photosynthetic performance and early growth to climatic conditions, and supports pleiotropism as a major cause of co‐locations of quantitative trait loci for these highly polygenic traits.     

Neoplastic Pigment Cells Induced by N-Methyl-N-nitrosourea (MNU) in Xiphophorus and Genetic Control of Their Terminal Differentiation

Neoplastic pigment cells can be induced by N-methyl-N-nitrosourea (MNU) in certain genotypes of the fish Xiphophorus that never develop such cells spontaneously. In some, the neoplastic cells retain their incompletely differentiated stage and proliferate, apparently due to unrestrained division, into malignant pigment cell neoplasms ('melanomata'). In other fish most of the neoplastic pigment cells become terminally differentiated and form harmless 'hyperplastic foci'. Terminal differentiation of MNU-induced neoplastic pigment cells appears to be predominantly controlled by a gene complex designated 'differentiation' (Diff).     

Biochemical Assay-Based Selectivity Profiling of Clinically Relevant Kinase Inhibitors on Mutant Forms of EGF Receptor

Gefitinib and erlotinib are potent EGFR tyrosine kinase inhibitors (potentially) useful for the treatment of non-small-cell lung cancer (NSCLC). Clinical responses, however, in NSCLC patients have been linked to the presence of certain activating mutations of EGFR. We used an ELISA-based biochemical assay to confirm the selective inhibitory efficacy of gefitinib and erlotinib on the activated mutant receptor. Our results are in line with the clinical observations providing evidence for the predictive power of the kinase assay. Four additional compounds were also investigated: CI-1033 and EKB-569 had dramatic inhibitory effects on all EGFR forms, whereas PD153035 and AG1478 were active on wild-type and activating mutant protein. In docking simulations with wild-type EGFR, our inhibitory data are in good agreement with the binding scores. These data confirm that anilinoquinazolines are good starting structures for the next generation of selective drugs against mutant EGFR, whereas CI-1033 and EKB-569 may represent advances for patients with both wild-type and anilinoquinazoline-resistant mutant tumors.     

Abnormal and variable sex ratios in population samples of ladybirds

While most ladybird species are believed to show a conventional 1:1 sex ratio, population samples from five different species of ladybird have been found to show significant excesses of females. The species involved are Anatis ocellata, Exochomus quadripustulatus, Chilocorus renipustulatus, C. bipustulatus and C. nigritus. All possess neo-XY sex chromosome systems. It is possible that the excesses of females reflect the recombination of segments present at the ends of the neo-XY sex bivalent. If the products of recombination are more lethal in males than females, differences in sex ratio will result. An alternative hypothesis involves an interaction between Y-linked factors and maternally inherited factors, possibly of a transposable element type. The maintenance of such excesses of females in several species, in different taxonomic groups within the Coccinellidae, and the presence of differences in different populations of one of the species, must reflect a selective advantage for these excesses in natural populations of these species.     

Zur Deutung der Carapaxfurchen der Astacidea (Crustacea, Decapoda)

The carapace grooves of decapod Crustacea are hitherto considered as remnants of somit boundaries. This hypothesis is rejected for theoretical reasons and on the basis of morphological studies of recent crayfishes and lobsters. The grooves are recognized as mechanically induced secondary structures resulting from the attachment of different muscles to the carapace. The grooves can be used for the diagnosis of certain systematic groups, but are of little value for phylogenetic considerations.     

The birth of an endemic species flock: demographic history of the Bellamya group (Gastropoda,Viviparidae) in Lake Malawi

Changes in habitat stability may significantly shape evolutionary patterns and processes in ancient lakes. In the present study, we use a hierarchical combination of molecular phylogenetic and coalescent approaches to investigate the evolutionary history of the endemic species of the gastropod genus Bellamya in the African rift‐lake Malawi. By integrating our findings with reported palaeontological and palaeolimnological data, we demonstrate that all but one evolutionary lineage of the Pliocene Bellamya fauna in Lake Malawi became extinct. Coalescent analyses indicate that the modern radiation underwent both a sudden demographic and a spatial expansion after a genetic bottleneck. We argue that a reflooding of the lake after severe Pleistocene low stands offers a straightforward explanation for this pattern and may have triggered speciation processes in the modern endemic Bellamya radiation in Lake Malawi. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 130–143.