scholarly journals How plants minimize somatic evolution

2021 ◽  
Author(s):  
Máté Kiss ◽  
Gergely J. Szöllősi ◽  
Imre Derényi
Keyword(s):  
Plant Evolution ◽  
Recent Experimental Data ◽  
Remarkable Property ◽  
Meristematic Tissue ◽  
Replication Errors ◽  
Slow Pace ◽  
Cell Divisions ◽  
Somatic Evolution ◽  
Apical Buds ◽  
Theoretical Minimum

A remarkable property of plants is their ability to accumulate mutations at a very slow pace despite their potentially long lifespans, during which they continually form buds, each with the potential to become a new branch. Because replication errors in cell division represent an unavoidable source of mutations, minimizing mutation accumulation requires the minimization of cell divisions. Here we show that there exists a well defined theoretical minimum for the branching cost, defined as the number of cell divisions necessary for the creation of each branch. Most importantly, we also show that this theoretical minimum can be closely approached by a simple pattern of cell divisions in the meristematic tissue of apical buds during the generation of novel buds. Both the optimal pattern of cell divisions and the associated branching cost are consistent with recent experimental data, suggesting that plant evolution has led to the discovery of this mechanism.

scholarly journals A comparison of humans and baboons suggests germline mutation rates do not track cell divisions

2019 ◽  
Author(s):  
Felix L. Wu ◽  
Alva Strand ◽  
Carole Ober ◽  
Jeffrey D. Wall ◽  
Priya Moorjani ◽  
...  
Keyword(s):  
Mutation Rate ◽  
Divergence Time ◽  
Germline Mutations ◽  
Mutation Rates ◽  
Papio Anubis ◽  
Male Bias ◽  
Olive Baboons ◽  
Replication Errors ◽  
Cell Divisions ◽  
Stem Cell Divisions

AbstractIn humans, most germline mutations are inherited from the father. This observation is widely interpreted as resulting from the replication errors that accrue during spermatogenesis. If so, the male bias in mutation should be substantially lower in a closely related species with similar rates of spermatogonial stem cell divisions but a shorter mean age of reproduction. To test this hypothesis, we resequenced two 3–4 generation nuclear families (totaling 29 individuals) of olive baboons (Papio anubis), who reproduce at ~10 years of age on average. We inferred sex-specific mutation rates by analyzing the data in parallel with three three-generation human pedigrees (26 individuals). The mutation rate per generation in baboons is 0.55×10−8 per base pair, approximately half that of humans. Strikingly, however, the degree of male mutation bias is approximately 3:1, similar to that of humans; in fact, a similar male bias is seen across mammals that reproduce months, years or decades after birth. These results echo findings in humans that the male bias is stable with parental ages and cast further doubt on the assumption that germline mutations track cell divisions. Our mutation rate estimates for baboons raise a further puzzle in suggesting a divergence time between apes and Old World Monkeys of 67 My, too old to be consistent with the fossil record; reconciling them now requires not only a slowdown of the mutation rate per generation in humans but also in baboons.

scholarly journals Germline replications and somatic mutation accumulation are independent of vegetative life span in Arabidopsis

2016 ◽  
Vol 113 (43) ◽  
pp. 12226-12231 ◽  
Author(s):  
J. Matthew Watson ◽  
Alexander Platzer ◽  
Anita Kazda ◽  
Svetlana Akimcheva ◽  
Sona Valuchova ◽  
...  
Keyword(s):  
Life Span ◽  
Vegetative Growth ◽  
Somatic Mutations ◽  
Concomitant Increase ◽  
Telomeric Dna ◽  
Replication Errors ◽  
Quiescent Cells ◽  
Cell Divisions ◽  
Hierarchical Arrangement ◽  
Cell Organization

In plants, gametogenesis occurs late in development, and somatic mutations can therefore be transmitted to the next generation. Longer periods of growth are believed to result in an increase in the number of cell divisions before gametogenesis, with a concomitant increase in mutations arising due to replication errors. However, there is little experimental evidence addressing how many cell divisions occur before gametogenesis. Here, we measured loss of telomeric DNA and accumulation of replication errors in Arabidopsis with short and long life spans to determine the number of replications in lineages leading to gametes. Surprisingly, the number of cell divisions within the gamete lineage is nearly independent of both life span and vegetative growth. One consequence of the relatively stable number of replications per generation is that older plants may not pass along more somatically acquired mutations to their offspring. We confirmed this hypothesis by genomic sequencing of progeny from young and old plants. This independence can be achieved by hierarchical arrangement of cell divisions in plant meristems where vegetative growth is primarily accomplished by expansion of cells in rapidly dividing meristematic zones, which are only rarely refreshed by occasional divisions of more quiescent cells. We support this model by 5-ethynyl-2′-deoxyuridine retention experiments in shoot and root apical meristems. These results suggest that stem-cell organization has independently evolved in plants and animals to minimize mutations by limiting DNA replication.

scholarly journals Mutation Vulnerability Characterizes Human Cancer Genes

2018 ◽  
Author(s):  
Yong Fuga Li ◽  
Fuxiao Xin
Keyword(s):  
Human Cancer ◽  
Hot Spot ◽  
Cancer Genes ◽  
Replication Errors ◽  
Somatic Evolution ◽  
Dna Mutations ◽  
Human Genes ◽  
Cancer Mutations ◽  
Random Patterns ◽  
Dna Replication Errors

AbstractRecent studies by Tomasetti et al. revealed that the risk disparity among different types of cancer is mainly determined by inherent patterns in DNA replication errors rather than environmental factors. In this study we reveal that inherent patterns of DNA mutations plays a similar role in cancer at the molecular level. Cancer results from stochastic DNA mutations, yet non-random patterns of cancer mutations emerge when we look across hundreds of cancer genomes. Over 500 cancer genes have been identified to date as the hot spot genes of cancer mutations. It is generally believed that these gene are mutated more frequently because they reside in functionally important pathways and are hence selected during the somatic evolution process of tumor progression. This theory however does not explain why many genes in the same pathways of cancer genes are not mutated in cancer. In this study, we challenge this view by showing that the inherent patterns of spontaneous mutations of human genes not only distinguish cancer causing genes and non-cancer genes but also shapes the mutation profile of cancer genes at the sub-gene level.

scholarly journals Distinct within-host bacterial populations ensure function, colonization and transmission in leaf symbiosis

2021 ◽  
Author(s):  
Tessa Acar ◽  
Sandra Moreau ◽  
Olivier Coen ◽  
Frédéric De Meyer ◽  
Olivier Leroux ◽  
...  
Keyword(s):  
Shoot Meristem ◽  
Bacterial Suspension ◽  
Flagellar Motility ◽  
Meristematic Tissue ◽  
Bacterial Populations ◽  
Tissue Specific ◽  
Apical Buds ◽  
Symbiont Transmission ◽  
Evolutionary Robustness ◽  
Specific Regulation

AbstractHereditary symbioses have the potential to drive transgenerational effects, yet the mechanisms responsible for transmission of heritable plant symbionts are still poorly understood. The leaf symbiosis between Dioscorea sansibarensis and the bacterium Orrella dioscoreae offers an appealing model system to study how heritable bacteria are transmitted to the next generation. Here, we demonstrate that inoculation of apical buds with a bacterial suspension is sufficient to colonize newly-formed leaves and propagules, and to ensure transmission to the next plant generation. Flagellar motility is not required for movement inside the plant, but is important for the colonization of new hosts. Further, stringent tissue-specific regulation of putative symbiotic functions highlight the presence of two distinct subpopulations of bacteria in the leaf gland and at the shoot meristem. We propose that bacteria in the leaf gland dedicate resources to symbiotic functions, while dividing bacteria in the shoot tip ensure successful colonization of meristematic tissue, glands and propagules. Compartmentalization of intra-host populations, together with tissue-specific regulation may serve as a robust mechanism for the maintenance of mutualism in leaf symbiosis.ImportanceSeveral plant species form associations with bacteria in their leaves, called leaf symbiosis. These associations are highly specific, but the mechanisms responsible for symbiont transmission are poorly understood. Using the association between the yam species Dioscorea sansibarensis and Orrella dioscoreae as a model leaf symbiosis, we provide experimental evidence that bacteria are transmitted vertically and distributed to specific leaf structures via association with shoot meristems. Flagellar motility is required for initial infection, but does not contribute to spread within host tissue. We also provide evidence that bacterial subpopulations at the meristem or in the symbiotic leaf gland differentially express key symbiotic genes. We argue that this separation of functional symbiont populations, coupled to tight control over bacterial infection and transmission, explain the evolutionary robustness of leaf symbiosis. These findings may provide insights into how plants may recruit and maintain beneficial symbionts at the leaf surface.

scholarly journals Cancer Risk and the Somatic Cell Lineage Tree

2020 ◽  
Author(s):  
Imre Derényi ◽  
Márton C. Demeter ◽  
Gergely J. Szöllősi
Keyword(s):  
Cancer Research ◽  
Analytical Formula ◽  
Cell Lineage ◽  
Driver Mutations ◽  
Cell Divisions ◽  
Somatic Evolution ◽  
Lineage Tree ◽  
Multicellular Organisms ◽  
Risk Of Cancer ◽  
Simple Analytical Formula

All the cells of a multicellular organism are the product of cell divisions that trace out a single binary tree, the so-called cell lineage tree. Because cell divisions are accompanied by replication errors, the shape of the cell lineage tree is one of the key determinants of how somatic evolution, which can potentially lead to cancer, proceeds. Cancer initiation usually requires the accumulation of a certain number of driver mutations. By mapping the accumulation of driver mutations into a graph theoretical problem, we show that in leading order of the mutation rate the probability of collecting a given number of driver mutations depends only on the distribution of the lineage lengths (irrespective of any other details of the cell lineage tree), and we derive a simple analytical formula for this probability. Our results are crucial in understanding how natural selection can shape the cell lineage trees of multicellular organisms in order to reduce their lifetime risk of cancer. In particular, our results highlight the significance of the longest cell lineages. Our analytical formula also provides a tool to quantify cancer susceptibility in theoretical models of tissue development and maintenance, as well as for empirical data on cell linage trees.Significance StatementA series of cell divisions starting from a single cell produce and maintain tissues of multicellular organisms. Somatic evolution, including the development of cancer, takes place along the cell lineage tree traced out by these cell divisions. A fundamental question in cancer research is how the lifetime risk of cancer depends on the properties of an arbitrary cell lineage tree. Here we show that for small mutation rates (which is the case in reality) the distribution of the lineage lengths alone determines cancer risk, and that this risk can be described by a simple analytical formula. Our results have far-reaching implications not only for cancer research, but also for evolutionary biology in general.

Stimulated Virus Production in Vinblastine and Cytochalasin-Induced Multinucleate Cells

1970 ◽  
Vol 28 ◽  
pp. 186-187
Author(s):  
Krishan Awtar
Keyword(s):  
Cell Division ◽  
Normal Cell ◽  
Virus Production ◽  
Multinucleate Cells ◽  
Daughter Cells ◽  
Cell Divisions ◽  
Nuclear Membranes ◽  
Division 2 ◽  
Vinblastine Sulfate

Exposure of cells to low sublethal but mitosis-arresting doses of vinblastine sulfate (Velban) results in the initial arrest of cells in mitosis followed by their subsequent return to an “interphase“-like stage. A large number of these cells reform their nuclear membranes and form large multimicronucleated cells, some containing as many as 25 or more micronuclei (1). Formation of large multinucleate cells is also caused by cytochalasin, by causing the fusion of daughter cells at the end of an otherwise .normal cell division (2). By the repetition of this process through subsequent cell divisions, large cells with 6 or more nuclei are formed.

Fusion and Breakup Reactions of 17S + 208Pb and 15C + 232ThHalo Nuclei Systems

2015 ◽  
Vol 11 (2) ◽  
pp. 2972-2978
Author(s):  
Fouad A. Majeed ◽  
Yousif A. Abdul-Hussien
Keyword(s):  
Experimental Data ◽  
Cross Section ◽  
Fusion Reaction ◽  
Fusion Cross Section ◽  
Reaction Cross ◽  
Recent Experimental Data ◽  
Barrier Distribution ◽  
Coupled Channel ◽  
Total Fusion ◽  
Full Quantum

In this study the calculations of the total fusion reaction cross section have been performed for fusion reaction systems 17F + 208Pb and 15C + 232Th which involving halo nuclei by using a semiclassical approach.The semiclassical treatment is comprising the WKB approximation to describe the relative motion between target and projectile nuclei, and Continuum Discretized Coupled Channel (CDCC) method to describe the intrinsic motion for both target and projectile nuclei. For the same of comparsion a full quantum mechanical clacualtions have been preforemd using the (CCFULL) code. Our theorticalrestuls are compared with the full quantum mechaincialcalcuations and with the recent experimental data for the total fusion reaction  checking the stability of the distancesThe coupled channel calculations of the total fusion cross section σfus, and the fusion barrier distribution Dfus. The comparsion with experiment proves that the semiclassiacl approach adopted in the present work reproduce the experimental data better that the full quantal mechanical calcautions. 

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