Gene expression during late embryogenesis in pea (Pisum sativum L)

A thesis submitted by Melinda Jane Mayer, B.Sc.(Bristol) in accordance with the requirements of the University of Durham for the degree of Doctor of Philosophy. Department of Biological Sciences, August 1993.Two cDNA libraries were constructed from desiccating pea cotyledons. Differential screening of the libraries with cDNA from an earlier developmental stage (physiological maturity) demonstrated that the abundant message population during dehydration shows some noticeable differences to the message populations present before desiccation. Clones hybridising to a polyubiquitin probe were isolated from a cDNA library. These clones were identified as messages for the two types of ubiquitin extension proteins (with 52 and 79 residue tails), already characterised in other species as being involved in ribosome biogenesis. The pea ubiquitin extension tail amino acid sequences showed considerable homology to tails from other plants, animals, yeast and protozoa, including a nuclear localisation site and a putative zinc-binding nucleic acid binding domain, the positions of which are conserved within the tail sequences. Sequencing of a second polyubiquitin cDNA from pea leaf demonstrated that pea contains a ubiquitin multigene family of at least four members. The expression of several genes associated with plant response to stress and two abundant seed messages (Leg A and J) was examined in developing and dehydrating cotyledons and axes. This confirmed conspicuous variations in the message levels of the genes examined as the cotyledons aged, with different members of the ubiquitin and legumin multigene families showing differential expression with age. It was also demonstrated that the expression pattern of certain messages in the cotyledons was different to that in the axes and other seed tissues. This was confirmed by an analysis of total and albumin protein fractions in cotyledons and axes. The effect on specific message and protein levels of premature desiccation treatments indicated that the temporal expression of several seed genes is related to the state of hydration of the seed, artificial desiccation leading to premature maturation. Seed storage protein message and protein levels were especially increased by premature desiccation. Legumin seed storage protein messages were also shown to be responsive to exogenous ABA applied to immature cotyledons during the seed filling stage. However, the other stress-related messages examined in pea (ubiquitin and a pea putative metallothionein) were not responsive to exogenous ABA at this developmental stage

Gender-Specific Effects of Unemployment on Family Formation: A Cross-National Perspective

This paper investigates the impact of unemployment on the propensity to start a family. Unemployment is accompanied by bad occupational prospects and impending economic deprivation, placing the well-being of a future family at risk. I analyze unemployment at the intersection of state-dependence and the reduced opportunity costs of parenthood, distinguishing between men and women across a set of welfare states. Using micro-data from the European Community Household Panel (ECHP), I apply event history methods to analyze longitudinal samples of first-birth transitions in France, Finland, Germany, and the UK (1994-2001). The results highlight spurious negative effects of unemployment on family formation among men, which can be attributed to the lack of breadwinner capabilities in the inability to financially support a family. Women, in contrast, show positive effects of unemployment on the propensity to have a first child in all countries except France. These effects prevail even after ontrolling for labour market and income-related factors. The findings are pronounced in Germany and the UK where work-family conflicts are the cause of high opportunity costs of motherhood, and the gender-specific division of labour is still highly traditional. Particularly among women with a moderate and low level of education, unemployment clearly increases the likelihood to have a first child

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Green evolution and dynamic adaptations revealed by genomes of the marine picoeukaryotes Micromonas.

International audiencePicoeukaryotes are a taxonomically diverse group of organisms less than 2 micrometers in diameter. Photosynthetic marine picoeukaryotes in the genus Micromonas thrive in ecosystems ranging from tropical to polar and could serve as sentinel organisms for biogeochemical fluxes of modern oceans during climate change. These broadly distributed primary producers belong to an anciently diverged sister clade to land plants. Although Micromonas isolates have high 18S ribosomal RNA gene identity, we found that genomes from two isolates shared only 90% of their predicted genes. Their independent evolutionary paths were emphasized by distinct riboswitch arrangements as well as the discovery of intronic repeat elements in one isolate, and in metagenomic data, but not in other genomes. Divergence appears to have been facilitated by selection and acquisition processes that actively shape the repertoire of genes that are mutually exclusive between the two isolates differently than the core genes. Analyses of the Micromonas genomes offer valuable insights into ecological differentiation and the dynamic nature of early plant evolution