Molecular Mechanisms of DNA Damage and Repair: Progress in Plants

Dedicated to Prof. Jan H. J. Hoeijmakers.

Referee: Dr. Nawin C. Mishra, Professor of Genetics, University of South Carolina, Department of Biological Sciences, Columbia, SC 29208

Despite stable genomes of all living organisms, they are subject to damage by chemical and physical agents in the environment (e.g., UV and ionizing radiations, chemical mutagens, fungal and bacterial toxins, etc.) and by free radicals or alkylating agents endogenously generated in metabolism. DNA is also damaged because of errors during its replication. The DNA lesions produced by these damaging agents could be altered base, missing base, mismatch base, deletion or insertion, linked pyrimidines, strand breaks, intra- and inter-strand cross-links.     

Conservation of telomere protein complexes: shuffling through evolution

The rapid evolution of telomere proteins has hindered identification of orthologs from diverse species and created the impression that certain groups of eukaryotes have largely non-overlapping sets of telomere proteins. However, the recent identification of additional telomere proteins from various model organisms has dispelled this notion by expanding our understanding of the composition, architecture and range of telomere protein complexes present in individual species. It is now apparent that versions of the budding yeast CST complex and mammalian shelterin are present in multiple phyla. While the precise subunit composition and architecture of these complexes vary between species, the general function is often conserved. Despite the overall conservation of telomere protein complexes, there is still considerable species-specific variation, with some organisms having lost a particular subunit or even an entire complex. In some cases, complex components appear to have migrated between the telomere and the telomerase RNP. Finally, gene duplication has created telomere protein paralogs with novel functions. While one paralog may be part of a conserved telomere protein complex and have the expected function, the other paralog may serve in a completely different aspect of telomere biology.     

Redox regulation and oxidant activation of heme oxygenase-1

The ultraviolet A (UVA, 320–400 nm) component of sunlight has the potential to generate an oxidative stress in cells and tissue so that antioxidants (both endogenous and exogenous) strongly influence the biological effects of UVA. The expression of several genes (including heme oxygenase-1, HO-1; collagenase; the CL100 phosphatase and the nuclear oncogenes, c-fos and c-jun) is induced following physiological doses of UVA to cells and this effect can be strongly enhanced by removing intracellular glutathione or enhancing singlet oxygen lifetime. We have observed that heme is released from microsomal heme-containing proteins by UVA and other oxidants and that activation of HO-1 expression by UVA correlates with levels of heme release. UVA radiation also leads to an increase in labile iron pools (either directly or via HO-1) and eventual increases in ferritin levels. The role of heme oxygenase in protection of skin fibroblasts is probably an emergency inducible defense pathway to remove heme liberated by oxidants. The slower increase in ferritin levels is an adaptive response which serves to keep labile iron pools low and thereby reduce Fenton chemistry and oxidant-induced chain reactions involving lipid peroxidation. In keratinocytes, the primary target of UVA radiation, heme oxygenase levels are constitutively high (because of HO-2 expression). Since there is a corresponding increase in basal levels of ferritin the epidermis appears to be well protected constitutively against the oxidative stress generated by UVA.     

Agrobacterium as a tool for gene transfer in woody species: The state of the art and practical perspectives. A review

Abstract

The Agrobacterium-mediated ability to transfer genes into organisms without sexual crossing provides breeders with new opportunities to improve the efficiency of plant production. Gene transfer offers advantages over classical genetic manipulation since plants are improved without disruption of the integrity of their genomes. Several useful genes isolated from microrganisms and affecting pest resistance, rooting ability, hormonal metabolism etc., are now available. These genes can be easily cloned into suitable Ti and Ri derived plasmid vectors and transferred into woody species. The scarce ability of most fruit trees to regenerate the whole plant from in vitro-cultured cells remains the main obstacle to a wider use of gene transfer technology.     

Laser Microdissection (LM): Applications to plant materials

Abstract

In recent years, Laser Microdissection (LM), which has been widely used in animal biology, has been adapted to plant tissues. This short paper focuses on some technical aspects concerning plant sample preparation for LM technology, with particular attention to the application of gene expression and proteomics studies. Examples derived from the use of different LM methods are reported and their applications to plant–microbe interactions are explored.     

SOD2 gene polymorphism and muscle damage markers in elite athletes

Abstract

Exercise-induced oxidative stress is a state that primarily occurs in athletes involved in high-intensity sports when pro-oxidants overwhelm the antioxidant defense system to oxidize proteins, lipids, and nucleic acids. During exercise, oxidative stress is linked to muscle metabolism and muscle damage, because exercise increases free radical production. The T allele of the Ala16Val (rs4880 C/T) polymorphism in the mitochondrial superoxide dismutase 2 (SOD2) gene has been reported to reduce SOD2 efficiency against oxidative stress. In the present study we tested the hypothesis that the SOD2 TT genotype would be underrepresented in elite athletes involved in high-intensity sports and associated with increased values of muscle and liver damage biomarkers. The study involved 2664 Caucasian (2262 Russian and 402 Polish) athletes. SOD2 genotype and allele frequencies were compared to 917 controls. Muscle and liver damage markers [creatine kinase (CK), creatinine, alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP)] were examined in serum from 1444 Russian athletes. The frequency of the SOD2 TT genotype (18.6%) was significantly lower in power/strength athletes (n = 524) compared to controls (25.0%, p = 0.0076) or athletes involved in low-intensity sports (n = 180; 33.9%, p < 0.0001). Furthermore, the SOD2 T allele was significantly associated with increased activity of CK (females: p = 0.0144) and creatinine level (females: p = 0.0276; males: p = 0.0135) in athletes. Our data show that the SOD2 TT genotype might be unfavorable for high-intensity athletic events.