-
Frontiers in Plant Science 2020Gametophytic mutants share very small proportion of the total mutants generated by any mutagenic approach; even rarer are the fertilization-defective gametophytic... (Review)
Review
Gametophytic mutants share very small proportion of the total mutants generated by any mutagenic approach; even rarer are the fertilization-defective gametophytic mutants. They require an efficient and targeted strategy instead of 'brute force' screening approach. The classical gametophyte mutant screening method, mainly based on the segregation distortion, can distinguish gametophytic mutants from the others. However, the mutants pooled after the screening constitute both fertilization-defective and developmental-defective gametophytic mutants. Until recently, there has not been any straightforward way to screen the former from the latter. Additionally, most of the mutations affecting both gametes are lost during the screening process. The novel gametophyte screening approach tends to circumvent those shortcomings. This review discusses on the classical approach of gametophytic mutant screening and focuses on the novel approach on distinguishing fertilization-/developmental-defective gametophytic mutants (both male and female). It offers an empirical basis of screening such mutants by taking in the consideration of earlier studies on fertilization failure, initiation of seed coat formation, and fertilization recovery system in plants.
PubMed: 32714355
DOI: 10.3389/fpls.2020.00967 -
Cancer Research Sep 2023Oncogenic point mutants of isocitrate dehydrogenases 1 and 2 (IDH2) generate 2-hydroxyglutarate, which inhibits lysine demethylases and increases heterochromatin. Tumor...
Oncogenic point mutants of isocitrate dehydrogenases 1 and 2 (IDH2) generate 2-hydroxyglutarate, which inhibits lysine demethylases and increases heterochromatin. Tumor cells expressing IDH mutants are sensitive to PARP inhibitors (PARPi), offering an opportunity to eliminate IDH-driven tumor cells in therapy. Expression of an oncogenic IDH1 mutant in cells leads to aberrant heterochromatin formation at DNA breaks and impairs DNA repair through homologous recombination (HR), providing a possible explanation for the PARPi sensitivity of IDH mutant cells. However, a recent study published in Molecular Cell shows that IDH mutant tumors do not display the genomic alterations associated with HR defects. Instead, IDH mutants induce heterochromatin-dependent DNA replication stress. Furthermore, PARP is activated by the replication stress induced by IDH mutants and required for suppressing the ensuing DNA damage, providing an alternative model to explain the susceptibility of IDH mutant cells to PARPis. This study presents a new example of oncogene-induced and heterochromatin-dependent replication stress, and a role of PARP in the response to the stress, extending the molecular basis for PARP-targeted therapy.
Topics: Humans; Poly(ADP-ribose) Polymerase Inhibitors; Heterochromatin; Mutation; DNA Damage; Neoplasms; Isocitrate Dehydrogenase
PubMed: 37433029
DOI: 10.1158/0008-5472.CAN-23-2015 -
Journal of Evolutionary Biology Feb 2023Mutant dynamics in fragmented populations have been studied extensively in evolutionary biology. Yet, open questions remain, both experimentally and theoretically. Some...
Mutant dynamics in fragmented populations have been studied extensively in evolutionary biology. Yet, open questions remain, both experimentally and theoretically. Some of the fundamental properties predicted by models still need to be addressed experimentally. We contribute to this by using a combination of experiments and theory to investigate the role of migration in mutant distribution. In the case of neutral mutants, while the mean frequency of mutants is not influenced by migration, the probability distribution is. To address this empirically, we performed in vitro experiments, where mixtures of GFP-labelled ("mutant") and non-labelled ("wid-type") murine cells were grown in wells (demes), and migration was mimicked via cell transfer from well to well. In the presence of migration, we observed a change in the skewedness of the distribution of the mutant frequencies in the wells, consistent with previous and our own model predictions. In the presence of de novo mutant production, we used modelling to investigate the level at which disadvantageous mutants are predicted to exist, which has implications for the adaptive potential of the population in case of an environmental change. In panmictic populations, disadvantageous mutants can persist around a steady state, determined by the rate of mutant production and the selective disadvantage (selection-mutation balance). In a fragmented system that consists of demes connected by migration, a steady-state persistence of disadvantageous mutants is also observed, which, however, is fundamentally different from the mutation-selection balance and characterized by higher mutant levels. The increase in mutant frequencies above the selection-mutation balance can be maintained in small ( ) demes as long as the migration rate is sufficiently small. The migration rate above which the mutants approach the selection-mutation balance decays exponentially with . The observed increase in the mutant numbers is not explained by the change in the effective population size. Implications for evolutionary processes in diseases are discussed, where the pre-existence of disadvantageous drug-resistant mutant cells or pathogens drives the response of the disease to treatments.
Topics: Animals; Mice; Selection, Genetic; Models, Genetic; Mutation; Population Dynamics; Biological Evolution
PubMed: 36514852
DOI: 10.1111/jeb.14131 -
International Journal of Molecular... Oct 2022Mutation is a source of genetic diversity widely used in breeding programs for the acquisition of agronomically interesting characters in commercial varieties of the... (Review)
Review
Mutation is a source of genetic diversity widely used in breeding programs for the acquisition of agronomically interesting characters in commercial varieties of the species, as well as in the rest of crop species. Mutation can occur in nature at a very low frequency or can be induced artificially. Spontaneous or bud sport mutations in somatic cells can be vegetatively propagated to get an individual with the mutant phenotype. Unlike animals, plants have unlimited growth and totipotent cells that let somatic mutations to be transmitted to the progeny. On the other hand, in vitro tissue culture makes it possible to induce mutation in plant material and perform large screenings for mutant's selection and cleaning of chimeras. Finally, targeted mutagenesis has been boosted by the application of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas9 and Transcription activator-like effector nuclease (TALEN) editing technologies. Over the last few decades, environmental stressors such as global warming have been threatening the supply of global demand for food based on population growth in the near future. For this purpose, the release of new varieties adapted to such changes is a requisite, and selected or generated mutants by properly regulated mechanisms could be helpful to this task. In this work, we reviewed the most relevant mutations for breeding traits in species such as flowering time, self-compatibility, fruit quality, and disease tolerance, including new molecular perspectives in the present postgenomic era including CRISPR/Cas9 and TALEN editing technologies.
Topics: Animals; Gene Editing; CRISPR-Cas Systems; Transcription Activator-Like Effector Nucleases; Prunus; Plant Breeding; Mutation; Endonucleases; Genome, Plant
PubMed: 36362061
DOI: 10.3390/ijms232113273 -
PloS One 2022Lens culinaris is a proteinaceous food crop that is consumed worldwide for protein requirements. Mutation breeding has been used to improve protein content, yield, and...
Lens culinaris is a proteinaceous food crop that is consumed worldwide for protein requirements. Mutation breeding has been used to improve protein content, yield, and related traits, as well as to select highly desirable mutants that are economically significant. An investigation of genotypic variation in lentil germplasm was carried out using induced mutagenesis, with caffeine, ethyl methane sulfonate (EMS), lead nitrate, and cadmium nitrate as mutagens that resulted in 18 mutant lines in the M3 generation. For the present study, we analyzed the genetic diversity of lentil mutant lines using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and random amplified polymorphic DNA markers (RAPD). The heterozygosity of RAPD markers per primer ranged from 50.00-90.90% with an average of 71.04%. The genetic divergent analysis was performed using hierarchical clustering (UPGMA), exhibited that these mutant lines were classified mainly into five subpopulation or clusters. A close resemblance with highest genetic coefficient similarity (1.00) were observed between control and mutant H; between mutant M and E; between mutant Q and J2, while more divergent mutants were N2 with mutant B; and mutant R with mutant J1with least genetic coefficient similarity (0.22). Protein and mineral content (Fe, Zn and Cu) were increased significantly in some high yielding mutant lines concerning to the control plant, and showed polymorphic variations in polypeptide chains in terms of banding pattern. Stomatal morphology in high yielding mutants were perceived utilizing scanning electron microscopy (SEM), exhibiting variations in stomatal size, stomatal opening and number of stomata. The present study's promising mutant lines' biological, physiological, and molecular profiles provide a foundation for forthcoming preservation and consumption strategies to broaden the genetic diversity of the breeding population of lentil.
Topics: Lens Plant; Random Amplified Polymorphic DNA Technique; Genetic Markers; Caffeine; Sodium Dodecyl Sulfate; Plant Breeding; Mutagens; Methane; Genetic Variation
PubMed: 36279277
DOI: 10.1371/journal.pone.0274937 -
Journal of the American Society of... Jun 2022C3 glomerulopathy (C3G) is a heterogeneous group of chronic renal diseases characterized predominantly by glomerular C3 deposition and complement dysregulation....
BACKGROUND
C3 glomerulopathy (C3G) is a heterogeneous group of chronic renal diseases characterized predominantly by glomerular C3 deposition and complement dysregulation. Mutations in factor H-related (FHR) proteins resulting in duplicated dimerization domains are prototypical of C3G, although the underlying pathogenic mechanism is unclear.
METHODS
Using and assays, we performed extensive characterization of an FHR-1 mutant with a duplicated dimerization domain. To assess the FHR-1 mutant's association with disease susceptibility and renal prognosis, we also analyzed copy number variations and FHR-1 plasma levels in two Spanish C3G cohorts and in a control population.
RESULTS
Duplication of the dimerization domain conferred FHR-1 with an increased capacity to interact with C3-opsonized surfaces, which resulted in an excessive activation of the alternative pathway. This activation does not involve C3b binding competition with factor H. These findings support a scenario in which mutant FHR-1 binds to C3-activated fragments and recruits native C3 and C3b; this leads to formation of alternative pathway C3 convertases, which increases deposition of C3b molecules, overcoming FH regulation. This suggests that a balanced FHR-1/FH ratio is crucial to control complement amplification on opsonized surfaces. Consistent with this conceptual framework, we show that the genetic deficiency of FHR-1 or decreased FHR-1 in plasma confers protection against developing C3G and associates with better renal outcome.
CONCLUSIONS
Our findings explain how FHR-1 mutants with duplicated dimerization domains result in predisposition to C3G. They also provide a pathogenic mechanism that may be shared by other diseases, such as IgA nephropathy or age-related macular degeneration, and identify FHR-1 as a potential novel therapeutic target in C3G.
Topics: Blood Proteins; Complement C3; Complement C3b Inactivator Proteins; Complement Factor H; DNA Copy Number Variations; Disease Susceptibility; Glomerulonephritis, IGA; Humans; Prognosis
PubMed: 35545301
DOI: 10.1681/ASN.2021101318 -
BMC Plant Biology May 2022Leaf color mutants have reduced photosynthetic efficiency, which has severely negative impacts on crop growth and economic product yield. There are different chlorophyll...
BACKGROUND
Leaf color mutants have reduced photosynthetic efficiency, which has severely negative impacts on crop growth and economic product yield. There are different chlorophyll mutants in Arabidopsis and crops that can be used for genetic control and molecular mechanism studies of chlorophyll biosynthesis, chloroplast development and photoefficiency. Chlorophyll mutants in Brassica napus are mostly used for mapping and location research but are rarely used for physiological research. The chlorophyll-deficient mutant in this experiment were both genetically mapped and physiologically analyzed.
RESULTS
In this study, yellow leaf mutant of Brassica napus L. mutated by ethyl methyl sulfone (EMS) had significantly lower chlorophyll a, b and carotenoid contents than the wild type, and the net photosynthetic efficiency, stomatal conductance and transpiration rate were all significantly reduced. The mutant had sparse chloroplast distribution and weak autofluorescence. The granule stacks were reduced, and the shape was extremely irregular, with more broken stromal lamella. Transcriptome data analysis enriched the differentially expressed genes mainly in phenylpropane and sugar metabolism. The mutant was mapped to a 2.72 Mb region on A01 by using BSA-Seq, and the region was validated by SSR markers.
CONCLUSIONS
The mutant chlorophyll content and photosynthetic efficiency were significantly reduced compared with those of the wild type. Abnormal chloroplasts and thylakoids less connected to the stroma lamella appeared in the mutant. This work on the mutant will facilitate the process of cloning the BnaA01.cd gene and provide more genetic and physiological information concerning chloroplast development in Brassica napus.
Topics: Arabidopsis; Brassica napus; Chlorophyll; Chlorophyll A; Chromosome Mapping; Photosynthesis; Plant Leaves
PubMed: 35585493
DOI: 10.1186/s12870-022-03630-9 -
Current Protocols Nov 2022Forward genetics is used to identify the genetic basis for a phenotype. The approach involves identifying a mutant organism exhibiting a phenotype of interest and then...
Forward genetics is used to identify the genetic basis for a phenotype. The approach involves identifying a mutant organism exhibiting a phenotype of interest and then mapping the causative locus or gene. Bulked-segregant analysis (BSA) is a quick and effective approach to map mutants using pools of mutants and wild-type plants from a segregating population to identify linkage of the mutant phenotype, and this approach has been successfully used in plants. Traditional linkage mapping approaches are outdated and time intensive, and can be very difficult. With the highly evolved development and reduction in cost of high-throughput sequencing, this new approach combined with BSA has become extremely effective in multiple plant species, including Zea mays (maize). While the approach is incredibly powerful, careful experimental design, bioinformatic mapping techniques, and interpretation of results are important to obtain the desired results in an effective and timely manner. Poor design of a mapping population, limitations in bioinformatic experience, and inadequate understanding of sequence data are limitations of these approaches for the researcher. Here, we describe a straightforward protocol for mapping mutations responsible for a phenotype of interest in maize, using high-throughput sequencing and BSA. Specifically, we discuss relevant aspects of developing a mutant mapping population. This is followed by a detailed protocol for DNA preparation and analysis of short-read sequences to map and identify candidate causative mutations responsible for the mutant phenotype of interest. We provide command-line and perl scripts to complete the bioinformatic analysis of the mutant sequence data. This protocol lays out the design of the BSA, bioinformatic approaches, and interpreting the sequencing data. These methods are very adaptable to any forward genetics experiment and provide a step-by-step approach to identifying the genetic basis of a maize mutant phenotype. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Bulked-segregant analysis and high-throughput sequencing to map maize mutants.
Topics: Zea mays; High-Throughput Nucleotide Sequencing; Chromosome Mapping; Genetic Linkage; Phenotype
PubMed: 36350247
DOI: 10.1002/cpz1.591 -
Journal of Bacteriology Jul 2022The symbiont Vibrio fischeri uses motility to colonize its host. In numerous bacterial species, motility is negatively controlled by cyclic-di-GMP (c-di-GMP), which is...
The symbiont Vibrio fischeri uses motility to colonize its host. In numerous bacterial species, motility is negatively controlled by cyclic-di-GMP (c-di-GMP), which is produced by diguanylate cyclases (DGCs) with GGDEF domains and degraded by phosphodiesterases with either EAL or HD-GYP domains. To begin to decode the functions of the 50 Vibrio fischeri genes with GGDEF, EAL, and/or HD-GYP domains, we deleted each gene and assessed each mutant's migration through tryptone broth salt (TBS) soft agar medium containing or lacking magnesium (Mg) and calcium (Ca), which are known to influence V. fischeri motility. We identified 6, 13, and 16 mutants with altered migration in TBS-Mg, TBS, and TBS-Ca soft agar, respectively, a result that underscores the importance of medium conditions in assessing gene function. A biosensor-based assay revealed that Mg and Ca affected c-di-GMP levels negatively and positively, respectively; the severe decrease in c-di-GMP caused by Mg addition correlates with its strong positive impact on bacterial migration. A mutant defective for , a homolog of V. cholerae , exhibited a severe defect in migration across all conditions. Motility of a double mutant was also severely defective and could be restored by expression of "c-di-GMP-blind" alleles of master flagellar regulator . Together, this work sheds light on the genes and conditions that influence c-di-GMP-mediated control over motility in V. fischeri and provides a foundation for (i) assessing roles of putative c-di-GMP-binding proteins, (ii) evaluating other c-di-GMP-dependent phenotypes in V. fischeri, (iii) uncovering potential redundancy, and (iv) deciphering signal transduction mechanisms. Critical bacterial processes, including motility, are influenced by c-di-GMP, which is controlled by environment-responsive synthetic and degradative enzymes. Because bacteria such as Vibrio fischeri use motility to colonize their hosts, understanding the roles of c-di-GMP-modulating enzymes in controlling motility has the potential to inform on microbe-host interactions. We leveraged recent advances in genetic manipulation to generate 50 mutants defective for putative c-di-GMP synthetic and degradative enzymes. We then assessed the consequences on motility, manipulating levels of magnesium and calcium, which inversely influenced motility and levels of c-di-GMP. Distinct subsets of the 50 genes were required under the different conditions. Our data thus provide needed insight into the functions of these enzymes and environmental factors that influence them.
Topics: Agar; Aliivibrio fischeri; Bacterial Proteins; Biofilms; Calcium; Cyclic GMP; Escherichia coli Proteins; Gene Expression Regulation, Bacterial; Magnesium; Vibrio cholerae
PubMed: 35758751
DOI: 10.1128/jb.00109-22 -
PLoS Computational Biology Dec 2020A major challenge in evolutionary developmental biology is to understand how genetic mutations underlie phenotypic changes. In principle, selective pressures on the...
A major challenge in evolutionary developmental biology is to understand how genetic mutations underlie phenotypic changes. In principle, selective pressures on the phenotype screen the gene pool of the population. Teeth are an excellent model for understanding evolutionary changes in the genotype-phenotype relationship since they exist throughout vertebrates. Genetically modified mice (mutants) with abnormalities in teeth have been used to explore tooth development. The relationship between signaling pathways and molar shape, however, remains elusive due to the high intrinsic complexity of tooth crowns. This hampers our understanding of the extent to which developmental factors explored in mutants explain developmental and phenotypic variation in natural species that represent the consequence of natural selection. Here we combine a novel morphometric method with two kinds of data mining techniques to extract data sets from the three-dimensional surface models of lower first molars: i) machine learning to maximize classification accuracy of 22 mutants, and ii) phylogenetic signal for 31 Murinae species. Major shape variation among mutants is explained by the number of cusps and cusp distribution on a tooth crown. The distribution of mutant mice in morphospace suggests a nonlinear relationship between the signaling pathways and molar shape variation. Comparative analysis of mutants and wild murines reveals that mutant variation overlaps naturally occurring diversity, including more ancestral and derived morphologies. However, taxa with transverse lophs are not fully covered by mutant variation, suggesting experimentally unexplored developmental factors in the evolutionary radiation of Murines.
Topics: Animals; Biological Evolution; Machine Learning; Mice; Mice, Mutant Strains; Models, Anatomic; Molar; Phylogeny; Signal Transduction
PubMed: 33315865
DOI: 10.1371/journal.pcbi.1008436