10 research outputs found

    Chloroplasts around the plant cell cycle

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    Plastids arose from an endosymbiosis between a host cell and free-living bacteria. One key step during this evolutionary process has been the establishment of coordinated cell and symbiont division to allow the maintenance of organelles during proliferation of the host. However, surprisingly little is known about the underlying mechanisms. In addition, due to their central role in the cell's energetic metabolism and to their sensitivity to various environmental cues such as light or temperature, plastids are ideally fitted to be the source of signals allowing plants to adapt their development according to external conditions. Consistently, there is accumulating evidence that plastid-derived signals can impinge on cell cycle regulation. In this review, we summarize current knowledge of the dialogue between chloroplasts and the nucleus in the context of the cell cycle

    Essential role of the plant DNA polymerase theta for the repair of replication-associated DNA damage under standard and abiotic stress conditions

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    International audienceSafeguard of genome integrity is a key process in all living organisms. Due to their sessile lifestyle, plants are particularly exposed to all kinds of stress conditions that could induce DNA damage. However, very few genes involved in the maintenance of genome integrity are indispensable to plants' viability. One remarkable exception is the POLQ gene that encodes DNA polymerase theta (Pol θ), a non-replicative polymerase involved in Trans-Lesion Synthesis (TLS) during DNA replication and Double-Strand Breaks (DSB) repair. The Arabidopsis tebichi (teb) mutants, deficient for Pol θ, have been reported to display severe developmental defects, leading to the conclusion that Pol θ is required for normal plant development. However, this essential role of Pol θ in plants is challenged by contradictory reports regarding the phenotypic defects of teb mutants, and the recent finding that rice null mutants develop normally. Here we show that the phenotype of teb mutants is highly variable. Taking advantage of hypomorphic mutants for the replicative DNA polymerase , that display constitutive replicative stress, we show that Pol θ allows maintenance of meristem activity when DNA replication is partially compromised. Furthermore, we found that the phenotype of Pol θ mutants can be aggravated by modifying their growth conditions, suggesting that environmental conditions impact the basal level of replicative stress, and providing evidence for a link between plants' response to adverse conditions, and mechanisms involved in the maintenance of genome integrity

    Role of the Polymerase ϵ sub-unit DPB2 in DNA replication, cell cycle regulation and DNA damage response in Arabidopsis

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    International audienceFaithful DNA replication maintains genome stability in dividing cells and from one generation to the next. This is particularly important in plants because the whole plant body and reproductive cells originate from meristematic cells that retain their proliferative capacity throughout the life cycle of the organism. DNA replication involves large sets of proteins whose activity is strictly regulated, and is tightly linked to the DNA damage response to detect and respond to replication errors or defects. Central to this interconnection is the replicative polymerase DNA Polymerase ϵ (Pol ϵ) which participates in DNA replication per se, as well as replication stress response in animals and in yeast. Surprisingly, its function has to date been little explored in plants, and notably its relationship with DNA Damage Response (DDR) has not been investigated. Here, we have studied the role of the largest regulatory sub-unit of Arabidopsis DNA Pol ϵ: DPB2, using an over-expression strategy. We demonstrate that excess accumulation of the protein impairs DNA replication and causes endogenous DNA stress. Furthermore, we show that Pol ϵ dysfunction has contrasting outcomes in vegetative and reproductive cells and leads to the activation of distinct DDR pathways in the two cell types

    Constructing Cell-Free Expression Systems for Low-Cost Access.

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    Cell-free systems for gene expression have gained attention as platforms for the facile study of genetic circuits and as highly effective tools for teaching. Despite recent progress, the technology remains inaccessible for many in low- and middle-income countries due to the expensive reagents required for its manufacturing, as well as specialized equipment required for distribution and storage. To address these challenges, we deconstructed processes required for cell-free mixture preparation and developed a set of alternative low-cost strategies for easy production and sharing of extracts. First, we explored the stability of cell-free reactions dried through a low-cost device based on silica beads, as an alternative to commercial automated freeze dryers. Second, we report the positive effect of lactose as an additive for increasing protein synthesis in maltodextrin-based cell-free reactions using either circular or linear DNA templates. The modifications were used to produce active amounts of two high-value reagents: the isothermal polymerase Bst and the restriction enzyme BsaI. Third, we demonstrated the endogenous regeneration of nucleoside triphosphates and synthesis of pyruvate in cell-free systems (CFSs) based on phosphoenol pyruvate (PEP) and maltodextrin (MDX). We exploited this novel finding to demonstrate the use of a cell-free mixture completely free of any exogenous nucleotide triphosphates (NTPs) to generate high yields of sfGFP expression. Together, these modifications can produce desiccated extracts that are 203-424-fold cheaper than commercial versions. These improvements will facilitate wider use of CFS for research and education purposes.The authors acknowledge the funding support from EPRSC (EP/R014000/1, LCVD: Low-cost Cell- extract Viral Diagnostics, FGC was supported by LCVD project; BBSRC/EPSRC OpenPlant Synthetic Biology Research Centre Grant BB/ L014130/1 to JH. The authors acknowledge Dr. Khalid K. Alam, former postdoc at Northwestern University who shared tips and protocols on preservation strategies after lyophilization. FF was funded by Fondo de Desarrollo de Áreas Prioritarias - Center for Genome Regulation (ANID/FONDAP/ 15090007). FF and AA were founded by Proyecto Investigación Interdisciplinaria 2018 VRI. AA was funded by ANID National Doctoral Scholarship ID:21140714 , and ANID - Millennium Science Initiative Program - ICN17_022, ICGEB CRP/CHL19-01. AAdhikari and SV were supported by the Center on the Physics of Cancer Metabolism at Cornell University through Award Number 1U54CA210184-01 from the National Cancer Institute. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute or the National Institutes of Health. Funding from CONACyT A1-S-17269, DGAPA- PAPIIT IN225220 to SSN

    Distinctive and complementary roles of E2F transcription factors during plant replication stress responses

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    International audienceSurvival of living organisms is fully dependent on their maintenance of genome integrity, being permanently threatened by replication stress in proliferating cells. Although the plant DNA damage response (DDR) regulator SOG1 has been demonstrated to cope with replication defects, accumulating evidence points to other pathways functioning independent of SOG1. Here, we report the roles of the Arabidopsis E2FA and EF2B transcription factors, two well-characterized regulators of DNA replication, in plant response to replication stress. Through a combination of reverse genetics and chromatin immunoprecipitation approaches, we show that E2FA and E2FB share many target genes with SOG1, providing evidence for their involvement in the DDR. Analysis of double- and triple-mutant combinations revealed that E2FB, rather than E2FA, plays the most prominent role in sustaining plant growth in the presence of replication defects, either operating antagonistically or synergistically with SOG1. Conversely, SOG1 aids in overcoming the replication defects of E2FA/E2FB-deficient plants. Collectively, our data reveal a complex transcriptional network controlling the replication stress response in which E2Fs and SOG1 act as key regulatory factors
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