Molecular Foundations of Reproductive Lethality in Arabidopsis thaliana

The SeedGenes database (www.seedgenes.org) contains information on more than 400 genes required for embryo development in Arabidopsis. Many of these EMBRYO-DEFECTIVE (EMB) genes encode proteins with an essential function required throughout the life cycle. This raises a fundamental question. Why does elimination of an essential gene in Arabidopsis often result in embryo lethality rather than gametophyte lethality? In other words, how do mutant (emb) gametophytes survive and participate in fertilization when an essential cellular function is disrupted? Furthermore, why do some mutant embryos proceed further in development than others? To address these questions, we first established a curated dataset of genes required for gametophyte development in Arabidopsis based on information extracted from the literature. This provided a basis for comparison with EMB genes obtained from the SeedGenes dataset. We also identified genes that exhibited both embryo and gametophyte defects when disrupted by a loss-of-function mutation. We then evaluated the relationship between mutant phenotype, gene redundancy, mutant allele strength, gene expression pattern, protein function, and intracellular protein localization to determine what factors influence the phenotypes of lethal mutants in Arabidopsis. After removing cases where continued development potentially resulted from gene redundancy or residual function of a weak mutant allele, we identified numerous examples of viable mutant (emb) gametophytes that required further explanation. We propose that the presence of gene products derived from transcription in diploid (heterozygous) sporocytes often enables mutant gametophytes to survive the loss of an essential gene in Arabidopsis. Whether gene disruption results in embryo or gametophyte lethality therefore depends in part on the ability of residual, parental gene products to support gametophyte development. We also highlight here 70 preglobular embryo mutants with a zygotic pattern of inheritance, which provide valuable insights into the maternal-to-zygotic transition in Arabidopsis and the timing of paternal gene activation during embryo development

Systematic Review of Potential Health Risks Posed by Pharmaceutical, Occupational and Consumer Exposures to Metallic and Nanoscale Aluminum, Aluminum Oxides, Aluminum Hydroxide and Its Soluble Salts

Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007). Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of “total Al”assumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold. The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al+ 3 to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)+ 2 and Al(H2O)6 + 3] that after complexation with O2•−, generate Al superoxides [Al(O2•)](H2O5)]+ 2. Semireduced AlO2• radicals deplete mitochondrial Fe and promote generation of H2O2, O2 • − and OH•. Thus, it is the Al+ 3-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates. Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer\u27s disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants. The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances

Iberomeryx minor (Mammalia, Artiodactyla) from the Early Oligocene of Soulce (Canton Jura, NW Switzerland): systematics and palaeodiet

The primitive ruminant genus Iberomeryx is poorly documented, as it is essentially only known from rare occurrences of dental remains. Therefore, the phylogeny and palaeobiology of Iberomeryx remain rather enigmatic. Only two species have been described: the type species I. parvus from the Benara locality in Georgia, and the Western European species I. minor reported from France, Spain, and Switzerland. Iberomeryx savagei from India has recently been placed in the new genus Nalameryx. All these localities are dated to the Rupelian and correspond mainly to MP23 (European mammal reference level). Based on the short height of the tooth-crown and the bunoselenodont pattern of the molars, Iberomeryx has often been considered as a folivore/frugivore. The I. minor remains from Soulce (NW Switzerland) are preserved in Rupelian lacustrine lithographic limestones. One specimen from this locality represents the most complete mandible of the taxon with a partially persevered ramus. Moreover, the unpreserved portion of the mandible left an imprint in the sediment, permitting the reconstruction of the mandible outline. Based on a new description of these specimens, anatomical comparisons and Relative Warp Analysis (24 landmarks) of 94 mandibles (11 fossil and 83 extant) from 31 ruminant genera (10 fossil and 21 extant) and 40 species (11 fossil and 29 extant), this study attempts a preliminary discussion of the phylogeny and the diet of the species I. minor. The results permit to differentiate Pecora and Tragulina on the first principal component axis (first Relative warp) on behalf of the length of the diastema c/cheek teeth, the length of the premolars and the angular process. The mandible shape of I. minor is similar to those of the primitive Tragulina, but it differs somewhat from those of the extant Tragulidae, the only extant family in the Tragulina. This difference is essentially due to a stockier mandible and a deeper incisura vasorum. However, in consideration of the general pattern of its cheek teeth, I. minor as well as possibly Nalameryx should be considered to represent the only known primitive Tragulidae from the Oligocene. Moreover, I. minor should have been a selective browser (fruit and dicot foliage) but, similarly to small Hypertragulidae and Tragulidae, may also have exceptionally consumed animal matter