Maintenance Of Genome Integrity Dna Damage Sensing Signaling Repair And Replication In Plants

Environmental stresses and metabolic by-products can severely affect the integrity of genetic information by inducing DNA damage and impairing genome stability. As a consequence, plant growth and productivity are irreversibly compromised. To overcome genotoxic injury, plants have evolved complex strategies relying on a highly efficient repair machinery that responds to sophisticated damage perception/signaling networks. The DNA damage signaling network contains several key components: DNA damage sensors, signal transducers, mediators, and effectors. Most of these components are common to other eukaryotes but some features are unique to the plant kingdom. ATM and ATR are well-conserved members of PIKK family, which amplify and transduce signals to downstream effectors. ATM primarily responds to DNA double strand breaks while ATR responds to various forms of DNA damage. The signals from the activated transducer kinases are transmitted to the downstream cell-cycle regulators, such as CHK1, CHK2, and p53 in many eukaryotes. However, plants have no homologue of CHK1, CHK2 nor p53. The finding of Arabidopsis transcription factor SOG1 that seems functionally but not structurally similar to p53 suggests that plants have developed unique cell cycle regulation mechanism. The double strand break repair, recombination repair, postreplication repair, and lesion bypass, have been investigated in several plants. The DNA double strand break, a most critical damage for organisms are repaired non-homologous end joining (NHEJ) or homologous recombination (HR) pathway. Damage on template DNA makes replication stall, which is processed by translesion synthesis (TLS) or error-free postreplication repair (PPR) pathway. Deletion of the error-prone TLS polymerase reduces mutation frequencies, suggesting PPR maintains the stalled replication fork when TLS is not available. Unveiling the regulation networks among these multiple pathways would be the next challenge to be completed. Some intriguing issues have been disclosed such as the cross-talk between DNA repair, senescence and pathogen response and the involvement of non-coding RNAs in global genome stability. Several studies have highlighted the essential contribution of chromatin remodeling in DNA repair DNA damage sensing, signaling and repair have been investigated in relation to environmental stresses, seed quality issues, mutation breeding in both model and crop plants and all these studies strengthen the idea that components of the plant response to genotoxic stress might represent tools to improve stress tolerance and field performance. This focus issue gives researchers the opportunity to gather and interact by providing Mini-Reviews, Commentaries, Opinions, Original Research and Method articles which describe the most recent advances and future perspectives in the field of DNA damage sensing, signaling and repair in plants. A comprehensive overview of the current progresses dealing with the genotoxic stress response in plants will be provided looking at cellular and molecular level with multidisciplinary approaches. This will hopefully bring together valuable information for both plant biotechnologists and breeders.

Environmental stresses and metabolic by-products can severely affect the integrity of genetic information by inducing DNA damage and impairing genome stability. As a consequence, plant growth and productivity are irreversibly compromised. To overcome genotoxic injury, plants have evolved complex strategies relying on a highly efficient repair machinery that responds to sophisticated damage perception/signaling networks. The DNA damage signaling network contains several key components: DNA damage sensors, signal transducers, mediators, and effectors. Most of these components are common to other eukaryotes but some features are unique to the plant kingdom. ATM and ATR are well-conserved members of PIKK family, which amplify and transduce signals to downstream effectors. ATM primarily responds to DNA double strand breaks while ATR responds to various forms of DNA damage. The signals from the activated transducer kinases are transmitted to the downstream cell-cycle regulators, such as CHK1, CHK2, and p53 in many eukaryotes. However, plants have no homologue of CHK1, CHK2 nor p53. The finding of Arabidopsis transcription factor SOG1 that seems functionally but not structurally similar to p53 suggests that plants have developed unique cell cycle regulation mechanism. The double strand break repair, recombination repair, postreplication repair, and lesion bypass, have been investigated in several plants. The DNA double strand break, a most critical damage for organisms are repaired non-homologous end joining (NHEJ) or homologous recombination (HR) pathway. Damage on template DNA makes replication stall, which is processed by translesion synthesis (TLS) or error-free postreplication repair (PPR) pathway. Deletion of the error-prone TLS polymerase reduces mutation frequencies, suggesting PPR maintains the stalled replication fork when TLS is not available. Unveiling the regulation networks among these multiple pathways would be the next challenge to be completed. Some intriguing issues have been disclosed such as the cross-talk between DNA repair, senescence and pathogen response and the involvement of non-coding RNAs in global genome stability. Several studies have highlighted the essential contribution of chromatin remodeling in DNA repair. DNA damage sensing, signaling and repair have been investigated in relation to environmental stresses, seed quality issues, mutation breeding in both model and crop plants and all these studies strengthen the idea that components of the plant response to genotoxic stress might represent tools to improve stress tolerance and field performance. This focus issue gives researchers the opportunity to gather and interact by providing Mini-Reviews, Commentaries, Opinions, Original Research and Method articles which describe the most recent advances and future perspectives in the field of DNA damage sensing, signaling and repair in plants. A comprehensive overview of the current progresses dealing with the genotoxic stress response in plants will be provided looking at cellular and molecular level with multidisciplinary approaches. This will hopefully bring together valuable information for both plant biotechnologists and breeders.

In recent years, the study of the plant cell cycle has become of major interest, not only to scientists working on cell division sensu strictu , but also to scientists dealing with plant hormones, development and environmental effects on growth. The book The Plant Cell Cycle is a very timely contribution to this exploding field. Outstanding contributors reviewed, not only knowledge on the most important classes of cell cycle regulators, but also summarized the various processes in which cell cycle control plays a pivotal role. The central role of the cell cycle makes this book an absolute must for plant molecular biologists.

Genomic instability is a major threat to living organisms. To counteract the damaging effects posed by endogenous and environmental agents, such as chemicals or radiation, micro-organisms devote several percent of their genome to encode proteins that function in the repair and recombination of DNA. For many years, a relatively small group of scientists have carefully delineated the molecular mechanisms of these repair processes, using the simplest model systems available, namely Escherichia coli and Saccharomyces cerevisiae. These studies, which until recently had only moderate impact outside of the field, now provide the cornerstone for exciting new research into analogous processes in human cells. The reason for this is the revelation that the biochemical pathways for the accurate replication, repair and recombination of DNA have been conserved through evolution. New research shows that human cells use DNA repair mechanisms that are analogous to those found in bacteria to overcome the damaging effects of environmental mutagens and carcinogens. Of particular significance is the observation that certain cancers are caused by defects in DNA repair enzymes. For example, the human inherited non-polyposis colon cancer is now known to be caused by defects in the enzymes that repair DNA mismatches. Because much detailed information has been accumulated in studies of analogous mismatch repair proteins from bacteria, rapid progress can now be made.

"An indispensable source for researchers, teachers, and graduate and postgraduate students interested in mutation breeding and genetic engineering. It introduces readers to contemporary knowledge and state-of-the-art technologies in the field of mutation breeding, including fundamental mechanisms and applications. . . . It will provide new directions, and avenues for enhancement of food security and food quality by using the latest techniques for the 'mutation as breeding' approach." - From Prof. Jameel M. Al-Khayri, King Faisal University, Saudi Arabia This comprehensive three-volume set book aims to help combat the challenge of providing enough food for the world by the use of advanced genetic processes to improve crop production, both in quantity and quality. Volume 1: Mutagenesis and Crop Improvement discusses mutagenesis, cytotoxicity, and crop improvement, covering the processes, mutagenic effectiveness, and mechanisms. The volume emphasizes the improvement of agronomic characteristics by manipulating the genotype of plant species, resulting in increased productivity. Volume 2: Revolutionizing Plant Biology covers the use of mutagenesis and biotechnology to explore the variability of mutant genes for crop improvement. The chapters deal with in-vitro mutagenesis to exploit the somaclonal variations induced in cell culture and highlight the importance of in-vitro mutagenesis in inducing salt resistance, heat resistance, and drought resistance. Volume 3: Mechanisms for Genetic Manipulation of Plants and Plant Mutants reviews the genetic engineering techniques used to mutate genes and to incorporate them into different plant species of cereals, pulses, vegetables, and fruits. Also discussed are the principles of genetic engineering by which desired genes can be transferred from plants to animals to microorganisms and vice versa.

The DNA of all organisms is constantly being damaged by endogenous and exogenous sources. Oxygen metabolism generates reactive species that can damage DNA, proteins and other organic compounds in living cells. Exogenous sources include ionizing and ultraviolet radiations, carcinogenic compounds and environmental toxins among others. The discovery of multiple DNA lesions and DNA repair mechanisms showed the involvement of DNA damage and DNA repair in the pathogenesis of many human diseases, most notably cancer. These books provide a comprehensive overview of the interdisciplinary area of DNA damage and DNA repair, and their relevance to disease pathology. Edited by recognised leaders in the field, this two-volume set is an appealing resource to a variety of readers including chemists, chemical biologists, geneticists, cancer researchers and drug discovery scientists.

The First International Congress on DNA Damage and Repair was held in Rome, Italy, July 12-17, 1987. It was organized by the Italian Com mission for Nuclear Alternative Energy Sources. The subject of DNA damage and repair involves almost all the fields ofbidogical sciences. Some of the more prominent ones include carcino genesis, photobiology, radiation biology, aging, enzymology, genetics, and molecular biology. These individual fields have their own interna tional meetings and although the meetings often have sessions devoted to DNA repair, they do not bring together a wide diversity of international workers in the field to exchange ideas. The purpose of the Congress was to facilitate such an exchange among scientists representing many fields of endeavor and many countries. The 37 manuscripts in this volume, presented by the invited spea kers during the four and half days of the Congress, encompass the field of DNA damage and repair. They cover biological systems ranging from mo lecules to humans and deal with damages and repair after treatment of cells with various types of radiations, chemicals, and exogenous and en dogenous oxidative damages. The Congress and its Proceedings are dedicated to two international leaders in the field of DNA damage and repair, Alexander Hollaender of the United States and Adriano Buzzati Traverso of Italy. Hollaender, who died in December 1986, was one of the first investigators to recognize the damage to DNA was important in cell killing and mutagenesis. His early work indicated that cells could recover from radiation injury.

Genome Duplication provides a comprehensive and readable overview of the underlying principles that govern genome duplication in all forms of life, from the simplest cell to the most complex multicellular organism. Using examples from the three domains of life - bacteria, archaea, and eukarya - Genome Duplication shows how all living organisms store their genome as DNA and how they all use the same evolutionary-conserved mechanism to duplicate it: semi-conservative DNA replication by the replication fork. The text shows how the replication fork determines where organisms begin genome duplication, how they produce a complete copy of their genome each time a cell divides, and how they link genome duplication to cell division. Genome Duplication explains how mistakes in genome duplication are associated with genetic disorders and cancer, and how understanding genome duplication, its regulation, and how the mechanisms differ between different forms of life, is critical to the understanding and treatment of human disease.