GIP1 and GIP2 Contribute to the Maintenance of Genome Stability at the Nuclear Periphery.

The maintenance of genetic information is important in eukaryotes notably through mechanisms occurring at the nuclear periphery where inner nuclear membrane proteins and nuclear pore-associated components are key factors regulating the DNA damage response (DDR). However, this aspect of DDR regulation is still poorly documented in plants. We addressed here how genomic stability is impaired in the () double mutants showing defective nuclear shaping.

Corrigendum: The GIP Gamma-Tubulin Complex-Associated Proteins are Involved in Nuclear Architecture in .

[This corrects the article DOI: 10.3389/fpls.2013.

Mechanical Shielding in Plant Nuclei.

In animal single cells in culture, nuclear geometry and stiffness can be affected by mechanical cues, with important consequences for chromatin status and gene expression. This calls for additional investigation into the corresponding physiological relevance in a multicellular context and in different mechanical environments. Using the Arabidopsis root as a model system, and combining morphometry and micro-rheometry, we found that hyperosmotic stress decreases nuclear circularity and size and increases nuclear stiffness in meristematic cells.

MGO3 and GIP1 act synergistically for the maintenance of centromeric cohesion.

The control of genomic maintenance during S phase is crucial in eukaryotes. It involves the establishment of sister chromatid cohesion, ensuring faithful chromosome segregation, as well as proper DNA replication and repair to preserve genetic information. In animals, nuclear periphery proteins - including inner nuclear membrane proteins and nuclear pore-associated components - are key factors which regulate DNA integrity.

Arabidopsis MZT1 homologs GIP1 and GIP2 are essential for centromere architecture.

Centromeres play a pivotal role in maintaining genome integrity by facilitating the recruitment of kinetochore and sister-chromatid cohesion proteins, both required for correct chromosome segregation. Centromeres are epigenetically specified by the presence of the histone H3 variant (CENH3). In this study, we investigate the role of the highly conserved γ-tubulin complex protein 3-interacting proteins (GIPs) in Arabidopsis centromere regulation.

GIP/MZT1 proteins orchestrate nuclear shaping.

The functional organization of the nuclear envelope (NE) is only just emerging in plants with the recent characterization of NE protein complexes and their molecular links to the actin cytoskeleton. The NE also plays a role in microtubule nucleation by recruiting γ-Tubulin Complexes (γ-TuCs) which contribute to the establishment of a robust mitotic spindle. γ-tubulin Complex Protein 3 (GCP3)-interacting proteins (GIPs) have been identified recently as integral components of γ-TuCs.

The GIP gamma-tubulin complex-associated proteins are involved in nuclear architecture in Arabidopsis thaliana.

During interphase, the microtubular cytoskeleton of cycling plant cells is organized in both cortical and perinuclear arrays. Perinuclear microtubules (MTs) are nucleated from γ-Tubulin Complexes (γ-TuCs) located at the surface of the nucleus. The molecular mechanisms of γ-TuC association to the nuclear envelope (NE) are currently unknown.

The GCP3-interacting proteins GIP1 and GIP2 are required for γ-tubulin complex protein localization, spindle integrity, and chromosomal stability.

Microtubules (MTs) are crucial for both the establishment of cellular polarity and the progression of all mitotic phases leading to karyokinesis and cytokinesis. MT organization and spindle formation rely on the activity of γ-tubulin and associated proteins throughout the cell cycle. To date, the molecular mechanisms modulating γ-tubulin complex location remain largely unknown.

Plant γH2AX foci are required for proper DNA DSB repair responses and colocalize with E2F factors.

Cellular responses to DNA double-strand breaks (DSBs) are linked in mammals and yeasts to the phosphorylated histones H2AX (γH2AX) repair foci which are multiproteic nuclear complexes responsible for DSB sensing and signalling. However, neither the components of these foci nor their role are yet known in plants. In this paper, we describe the effects of γH2AX deficiency in Arabidopsis thaliana plants challenged with DSBs in terms of genotoxic sensitivity and E2F-mediated transcriptional responses.

Non-apoptotic programmed cell death with paraptotic-like features in bleomycin-treated plant cells is suppressed by inhibition of ATM/ATR pathways or NtE2F overexpression.

In plants, different forms of programmed cell death (PCD) have been identified, but they only partially correspond to those described for animals, which is most probably due to structural differences between animal and plant cells. Here, the results show that in tobacco BY-2 cells, bleomycin (BLM), an inducer of double-strand breaks (DSBs), triggers a novel type of non-apoptotic PCD with paraptotic-like features. Analysis of numerous PCD markers revealed an extensive vacuolization, vacuolar rupture, and chromatin condensation, but no apoptotic DNA fragmentation, fragmentation of the nuclei, or sensitivity to caspase inhibitors.

Ribonucleotide reductase regulation in response to genotoxic stress in Arabidopsis.

Ribonucleotide reductase (RNR) is an essential enzyme that provides dNTPs for DNA replication and repair. Arabidopsis (Arabidopsis thaliana) encodes three AtRNR2-like catalytic subunit genes (AtTSO2, AtRNR2A, and AtRNR2B). However, it is currently unclear what role, if any, each gene contributes to the DNA damage response, and in particular how each gene is transcriptionally regulated in response to replication blocks and DNA damage.

E2F factors rate controls the dual role of CDE/E2F composite element: a model of E2F-regulated gene expression in plant development.

The promoters of several E2F-regulated genes identified in plants contain a variety of E2F motifs, notably a composite element consisting of a "CDE-like element" C/GGCGG on one strand, described as repressor in animals, associated with an E2F element on the complementary strand. This detailed study throughout plant development using ribonucleotide reductase promoters, allows us to propose a model, where E2F and composite elements play a dual role. Such regulation is mainly conditioned by the availability of E2F factors in tissues and during the cell cycle in tobacco.

GeneFarm, structural and functional annotation of Arabidopsis gene and protein families by a network of experts.

Genomic projects heavily depend on genome annotations and are limited by the current deficiencies in the published predictions of gene structure and function. It follows that, improved annotation will allow better data mining of genomes, and more secure planning and design of experiments. The purpose of the GeneFarm project is to obtain homogeneous, reliable, documented and traceable annotations for Arabidopsis nuclear genes and gene products, and to enter them into an added-value database.