Contribution of cell and molecular biology and genetics to plant protection

Plants resist to the majority of their potential aggressors by opposing physical and chemical barriers: cell walls, secondary metabolites.... Phenomena of specific recognition between a plant variety and a pathovar induce on the one hand, a local (hypersensitive) reaction that tends to limit pathogen growth and, on the other hand, a cascade of signals that allows the activation of a non-specific general (systemic) resistance. The contribution of genetics to the fight against pathogens depends on the natural variability that comes from the co-evolution between plants and their aggressors. Many plant varieties resistant to one or several pathogens have been obtained and are cultivated. The use of biotechnology will facilitate the rapid generation of new, resistant cultivars and cultivars with multiple resistances. New methods in order to increase the efficiency and the durability of resistance are envisaged.     

The origins of molecular genetics

Journal of the History of Biology -     

The molecular genetics of collagen

In their Bioessays review ‘Current views of collagen degradation’, Gillian Murphy and John Reynolds gave an outline of the molecular structure of the members of the collagen family and described their traditional role in providing stable tissue frameworks.¹ This short review considers the relationship between the different members of that family and what gene structure reveals about their evolution. Mutation of the collagen structural genes has been discovered in patients suffering from brittle-bone syndrome and other inherited connective tissue disorders, and here I attempt to rationalize these results into an overall concept of collagen gene mutation and evolution.     

Present problems of somatic cell genetics]

A review of recent advances in genetics of somatic cells is given in the article. It contains three sections: 1) hybridization of somatic cells and its application to the mapping of genes and to the study of gene action; 2) relation of somatic cell genetics to genetic engineerings; 3) progress and perspectives of higher plant somatic cell genetics.     

The molecular genetics of Bardet-Biedl syndrome

Bardet-Biedl syndrome (BBS) has been shown to be a genetically heterogeneous disorder involving genes mapping to at least six known loci. One BBS gene (MKKS) has been identified and the form of the disorder caused by this gene is allelic to McKusick-Kaufman syndrome. MKKS codes for a putative chaperonin, suggesting that other BBS genes may also code for components of chaperone complexes or be substrates of chaperone function.     

The molecular genetics of Alzheimer's disease

The major pathological characteristic of Alzheimer's disease (AD) is the abnormal deposition of β-amyloid peptide (Aβ) in the brain. In some early onset cases, the disease develops because of mutations in the gene coding for β-amyloid precursor protein (βAPP). However, the majority of AD families in the early onset subgroup are linked to a locus on chromosome 14. The genetic analysis and age of onset correlates of both the βAPP gene and the chromosome 14 locus are discussed. We speculate on the mechanisms by which the βAPP mutations cause the disease and discuss recent advances in βAPP processing that may be relevant to the pathogenesis of the late-onset (common) form of the disease. In addition, we review the association of theAPOE locus with late-onset familial and nonfamilial disease. Further work is required to establish the effects of this locus on disease occurrence, age of onset, and progression. The molecular pathology of ApoE in relation to AD development and the identification of the chromosome 14 gene will greatly contribute to a general pathogenic model of AD, and will clarify the role of βAPP and its derivatives.     

The molecular genetics of crop domestication

Ten thousand years ago human societies around the globe began to transition from hunting and gathering to agriculture. By 4000 years ago, ancient peoples had completed the domestication of all major crop species upon which human survival is dependent, including rice, wheat, and maize. Recent research has begun to reveal the genes responsible for this agricultural revolution. The list of genes to date tentatively suggests that diverse plant developmental pathways were the targets of Neolithic "genetic tinkering," and we are now closer to understanding how plant development was redirected to meet the needs of a hungry world.     

The molecular genetics of male infertility

Spermatogenesis is an elaborate process involving both cell division and differentiation, and cell-cell interactions. Defects in any of these processes can result in infertility, and in some cases these can be genetic in cause. Mapping experiments have defined at least three regions of the human Y chromosome that are required for normal spermatogenesis. Two of these contain the genes encoding the RNA binding proteins RBM and DAZ, suggesting that the control of RNA metabolism is likely to be an important control point for human spermatogenesis. A similar analysis in mice has shown that at least two regions of the mouse Y chromosome are essential for spermatogenesis. Both genetic and reverse genetic approaches have been used to identify mouse autosomal genes required for spermatogenesis. These studies have shown that genes in a number of different pathways are essential for normal spermatogenesis, and also provide putative models of human infertility.     

The molecular genetics of European ancestry

In an earlier paper we proposed, on the basis of mitochondrial control region variation, that the bulk of modern European mitochondrial DNA(mtDNA) diversity had its roots in the European Upper Palaeolithic. Refining the mtDNA phylogeny and enlarging the sample size both within Europe and the Middle East still support this interpretation and indicate three separate phases of colonization: (i) the Early Upper Palaeolithic about 50,000 BP; (ii) the Late Upper Palaeolithic 11,000-14,000 BP; and (iii) the Neolithic from 8500 BP.     

The genetics and molecular genetics of terpene and sterol origami

Terpenes and sterols are complex molecules synthesized by equally complex biosynthetic pathways. Recent progress in using the tools of genetics, molecular genetics and genetic engineering to dissect triterpene metabolism in the cytosol, and terpene metabolism in the plastids, has opened up new strategies and avenues of investigation. Most importantly, these studies have enhanced our appreciation of the biological significance of these compounds for plants, and have revealed new secrets of this intriguing biochemistry for practical applications in agriculture and medicine.     

Applications of differential geometry to molecular genetics

A mathematical formalism is presented in which changes in information content of an evolving DNA (deoxyribonucleic acid) molecule may be described. The basic construct is a 65-dimensional differentiable manifold (the informational space-time manifold) in a coordinate structure such that the manifold points represent (i) the number of each codon type in a DNA molecule, and (ii) the evolutionary time of that DNA. It is shown that this manifold cannot be Euclidean but must be taken, at least conditionally, to be Riemannian. Evolutionary motions in the informational space-time manifold are initially postulated to be geodesics, and evolutionary equations-of-motion are elaborated. These equations are governed by an evolutionary field which is produced by the intrinsic structure of the manifold. The concept of genetic cosmology is introduced, and a manifold in which the evolutionary field is weak and depends only upon the evolutionary time is investigated. The nature of empirical input into genetic cosmology is discussed.Work supported by the U.S. Department of Energy.     

The molecular genetics of early human life

Molecular Genetics of Early Human Development(Human Molecular Genetics series), edited by T. Strachan, S. Lindsay and D.I. Wilson, Bios Scientific Publishers, 1997. £65 (xiv+265 pages) ISBN 1 859960 31 6