Myths about moths: a study in contrasts

The phenomenon of industrial melanism is the preeminent example of natural selection in textbooks and the popular media. Much of its fame stems from a set of pioneering and apparently definitive investigations by H.B.D. 'Bernard' Kettlewell in the early 1950s. There is a marked contrast in how the phenomenon and Kettlewell's work on it are perceived by the public and scientists. Tensions between these two perceptions have recently led to calls for the removal of the example from textbooks, and indeed allegations that Kettlewell committed fraud. This article (part of the Science in the Industrial Revolution series) will show that these charges are baseless and stem from a fundamental misunderstanding of the nature of science as a process.     

Expression of a begomoviral DNAβ gene in transgenic Nicotiana plants induced abnormal cell division

An increasing number ofmonopartite begomoviruses are being identified that a satellite molecule (DNAβ) is required to induce typical symptoms in host plants. DNAβ encodes a single gene (termed βCl) encoded in the complementary-sense. We have produced transgenic Nieotiana benthamiana and N. tabaeum plants expressing the βC1 gene of a DNAβ associated with Tomato yellow leaf curl China virus (TYLCCNV), under the control of the Cauliflower mosaic virus 35S promoter. Transgenic plants expressing 13C1 showed severe developmental abnormalities in both species. Microscopic analysis of sections of both transgenic and non-transgenic N. tabaeum leaves showed abnormal outgrowths of transgenic N. tabaeum to be due to disorganizedcell division (hyperplasia) of spongy and palisade parenchyma. Immuno-gold labeling of sections with a polyclonal antibody against the βC1 protein showed that the 13C 1 protein accumulated in the nuclei of cells. The possible biological function of the βC1 1protein was discussed.     

Growth propagation of yeast in linear arrays of microfluidic chambers over many generations

The growth of microorganisms is often confined in restricting geometries. In this work, we designed a device to study the growth propagation of budding yeast along linear arrays of microfluidic chambers. Vacuum assisted cell loading was used to seed cells of limited numbers in the up-most chambers of each linear array. Once loaded, cells grow until confluent and then overgrow, pushing some of the newborns into the neighboring downstream chamber through connection channels. Such a scenario repeats sequentially along the whole linear chamber arrays. We observed that the propagation speed of yeast population along the linear arrays was strongly channel geometry dependent. When the connection channel is narrow and long, the amount of cells delivered into the downstream chamber is small so that cells grow over several generations in the same chamber before passing into the next chamber. Consequently, a population growth of more than 50 generations could be observed along a single linear array. We also provided a mathematical model to quantitatively interpret the observed growth dynamics.