Specific panicle responses resulting from MSMA-induced straighthead sterility in rice

Straighthead is a physiological disorder of rice causing sterility. A particular characteristic of straighthead is panicles that remain upright because of the light weight of the unfilled grains, the hulls of which may be distorted into a crescent or parrot-beak shape. Monosodium methanearsenate (MSMA) was used in this study, to induce straighthead-like sterility symptoms in rice. Rating scales were developed to quantify the specific symptoms of straighthead (grain distortion, rachis curvature, panicle exsertion, and panicle weight), which were used to examine MSMA-induced straighthead in a greenhouse setting. Different rice cultivars were surveyed for their specific responses to MSMA, to identify targets for focus in rice breeding that differ in their responses. MSMA altered the pattern of anthesis so that flowering continued for a longer period of time although the initial flowering time and total panicle number were not affected. Early flowering panicles were less affected by MSMA than later flowering panicles. While all previous studies of MSMA-induced straighthead used MSMA applied at or before planting, a time course of MSMA application showed a time point for application at about the V4 (4-leaf) stage when the sterility symptoms were reduced and then an interval of time from about V6 to V8 when applications resulted in symptoms more severe than application at planting. A greenhouse temperature study demonstrated that lowering the temperature of the roots reduced the severity of the responses. MSMA is valuable as a trigger to induce a set of sterility symptoms so that the underlying physiological, biochemical, and genetic causes can be studied, and which may have implications for other sterility conditions.     

Molecular Exploration of the First-Century Tomb of the Shroud in Akeldama,Jerusalem

The Tomb of the Shroud is a first-century C.E. tomb discovered in Akeldama, Jerusalem, Israel that had been illegally entered and looted. The investigation of this tomb by an interdisciplinary team of researchers began in 2000. More than twenty stone ossuaries for collecting human bones were found, along with textiles from a burial shroud, hair and skeletal remains. The research presented here focuses on genetic analysis of the bioarchaeological remains from the tomb using mitochondrial DNA to examine familial relationships of the individuals within the tomb and molecular screening for the presence of disease. There are three mitochondrial haplotypes shared between a number of the remains analyzed suggesting a possible family tomb. There were two pathogens genetically detected within the collection of osteological samples, these were Mycobacterium tuberculosis and Mycobacterium leprae. The Tomb of the Shroud is one of very few examples of a preserved shrouded human burial and the only example of a plaster sealed loculus with remains genetically confirmed to have belonged to a shrouded male individual that suffered from tuberculosis and leprosy dating to the first-century C.E. This is the earliest case of leprosy with a confirmed date in which M. leprae DNA was detected.     

Strabismus Promotes Recruitment and Degradation of Farnesylated Prickle in Drosophila melanogaster Planar Polarity Specification

The core planar polarity proteins are required to specify the orientation of structures that are polarised in the plane of the epithelium. In the Drosophila melanogaster wing, the core proteins localise asymmetrically at either proximal or distal cell edges. Asymmetric localisation is thought to be biased by long-range cues, causing asymmetric complexes to become aligned with the tissue axes. Core proteins are then thought to participate in feedback interactions that are necessary to amplify asymmetry, and in order for such feedback interactions to operate correctly, the levels of the core proteins at junctions must be tightly regulated. We have investigated regulation of the core protein Prickle (Pk) in the pupal wing. The core protein Strabismus (Stbm) is required to recruit Pk into asymmetric complexes at proximal cell ends, and we report here that it also promotes proteasomal degradation of excess Pk, probably via a Cullin-1 dependent process. We also show for the first time that Pk is farnesylated in vivo, and this is essential for Pk function in the wing. Notably, farnesylation of Pk is necessary for it to be recruited into asymmetric complexes and function in feedback amplification, probably by reinforcing weak direct interactions between Stbm and Pk. Furthermore, farnesylation is also required for Stbm to promote proteasomal degradation of Pk. We propose that Stbm recruits farnesylated Pk into asymmetric complexes, but also promotes degradation of excess Pk that would otherwise perturb feedback amplification.     

The Role of Intuitive Ontologies in Scientific Understanding – the Case of Human Evolution

Psychological evidence suggests that laypeople understand the world around them in terms of intuitive ontologies which describe broad categories of objects in the world, such as ‘person’, ‘artefact’ and ‘animal’. However, because intuitive ontologies are the result of natural selection, they only need to be adaptive; this does not guarantee that the knowledge they provide is a genuine reflection of causal mechanisms in the world. As a result, science has parted ways with intuitive ontologies. Nevertheless, since the brain is evolved to understand objects in the world according to these categories, we can expect that they continue to play a role in scientific understanding. Taking the case of human evolution, we explore relationships between intuitive ontological and scientific understanding. We show that intuitive ontologies not only shape intuitions on human evolution, but also guide the direction and topics of interest in its research programmes. Elucidating the relationships between intuitive ontologies and science may help us gain a clearer insight into scientific understanding.     

Deltamethrin-Mediated Toxicity and Cytomorphological Changes in the Midgut and Nervous System of the Mayfly Callibaetis radiatus

Immature instars of mayflies are important constituents of the food web in aquatic ecosystems (especially in Neotropical regions) and they are among the most susceptible arthropods to pyrethroid insecticides. These insecticides have been recognized as important stressors of freshwater ecosystems, but their cellular effects in aquatic insects have been neglected. Here, we assessed the susceptibility to deltamethrin (a typical type II pyrethroid) as well as the deltamethrin-mediated cytomorphological changes in the central nervous system and midgut of the mayfly Callibaetis radiatus. While the deltamethrin LC₅₀ for 24h of exposure was of 0.60 (0.46–0.78) μg of a.i/L, the survival of C. radiatus was significantly reduced in deltamethrin concentrations ≥ 0.25 μg a.i/L at 96h of exposure. Sub-lethal deltamethrin exposure severely affected the cytomorphology of C. radiatus midgut (e.g., muscle layer retraction, cytoplasm vacuolation, nucleus and striated border disorganization) and also induced slight cytomorphological changes in the brain (e.g., presence of pyknotic nuclei) and in the thoracic ganglia (e.g., vacuolation of neurons and presence of pyknotic nuclei) of these insects. However, DNA damage was absent in all of these organs, suggesting that the sublethal cellular stress induced by deltamethrin might disrupt physiological processes (e.g., metabolism or electrical signal transmission) rather than cause cell death (e.g., apoptosis) in C. radiatus. Thus, our findings indicated that deltamethrin actions at cellular levels represent a clear indication of sublethal effects on the C. radiatus survival abilities.     

The capacity of the fourth chromosome of Drosophila melanogaster to establish end-to-end contacts with the other chromosomes in salivary-gland cells

When the fourth chromosome of Drosophila melanogaster is attached, as the result of an induced translocation, to 21A in 2L or 60E in 2R, its tip exhibits a marked capacity to pair end-to-end with the tips of the other chromosomes. In each of the translocations, about 59 per cent of the contacts involving the tip of 4 were with the tip of X. If this pairing preference reflects structural similarity, the tip of 4 is much more like the tip of X than that of any other chromosome. The significance of this phenomenon is discussed with respect to the standard pattern of end-to-end association in the Oregon-R wild-type stock that provided the control preparations. In the 4-2L rearrangement, the interaction of chromosome 4 with the tip of 2L (101E with 21A) led to pronounced puffing in subdivisions 21A and B, as was most strikingly manifested when the distal segments of 2L failed to synapse and the homologue of paternal origin showed a large puff whereas that of maternal origin (not carrying the fourth chromosome) remained unpuffed.This study was supported in part by a Research Grant (GM-10499) from the National Institutes of Health, U.S. Public Health Service.