An official website of the United States government
ABSTRACT Of the three types of cytoskeleton known in animals—actin, microtubules, and intermediate filaments—only actin and microtubules exist in plants. Both play important roles in cellular shaping, organelle movement, organization of the endomembrane system, and cell signaling. An emerging, but often overlooked role of the plant cytoskeleton is its dynamic and mutually influential interaction with the nucleus. Here, we summarize recent advances in understanding the role of the cytoskeleton in plant nuclear movement in different biological contexts, a role for nuclear envelope‐associated proteins in reorganizing the actin and microtubule cytoskeleton, and the molecular nature of the nucleus‐cytoskeleton interface and specific proteins contributing to it. In animals, the nucleoskeleton consists of the nuclear lamina, an intermediate‐filament meshwork underlying the nuclear envelope. Plants have evolved an equivalent of this structure, built by different types of proteins. Here, we highlight recent advances in understanding its filamentous organization, newly discovered protein interactions connecting it to nuclear pores, and exciting new evidence that—just like the animal lamina—the plant lamina is involved in chromatin reorganization and epigenetic changes. Together, these new developments create new opportunities toward a deeper understanding of this important regulatory connection between the cytoskeleton and the cell's largest organelle.
more »
« less
The nuclear lamina is required for proper development and nuclear shape distortion in tomato
Abstract The nuclear lamina in plant cells is composed of plant-specific proteins, including nuclear matrix constituent proteins (NMCPs), which have been postulated to be functional analogs of lamin proteins that provide structural integrity to the organelle and help stabilize the three-dimensional organization of the genome. Using genomic editing, we generated alleles for the three genes encoding NMCPs in cultivated tomato (Solanum lycopersicum) to determine if the consequences of perturbing the nuclear lamina in this crop species were similar to or distinct from those observed in the model Arabidopsis thaliana. Loss of the sole NMCP2-class protein was lethal in tomato but is tolerated in Arabidopsis. Moreover, depletion of NMCP1-type nuclear lamina proteins leads to distinct developmental phenotypes in tomato, including leaf morphology defects and reduced root growth rate (in nmcp1b mutants), compared with cognate mutants in Arabidopsis. These findings suggest that the nuclear lamina interfaces with different developmental and signaling pathways in tomato compared with Arabidopsis. At the subcellular level, however, tomato nmcp mutants resembled their Arabidopsis counterparts in displaying smaller and more spherical nuclei in differentiated cells. This result argues that the plant nuclear lamina facilitates nuclear shape distortion in response to forces exerted on the organelle within the cell.
more »
« less
- Award ID(s):
- 2022048
- PAR ID:
- 10440985
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Journal of Experimental Botany
- ISSN:
- 0022-0957
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract SPINDLY (SPY) is a novel nucleocytoplasmic protein O-fucosyltransferase that regulates target protein activity or stability via O-fucosylation of specific Ser/Thr residues. Previous genetic studies indicate that AtSPY regulates plant development during vegetative and reproductive growth by modulating gibberellin and cytokinin responses. AtSPY also regulates the circadian clock and plant responses to biotic and abiotic stresses. The pleiotropic phenotypes of spy mutants point to the likely role of AtSPY in regulating key proteins functioning in diverse cellular pathways. However, very few AtSPY targets are known. Here, we identified 88 SPY targets from Arabidopsis (Arabidopsis thaliana) and Nicotiana benthamiana via the purification of O-fucosylated peptides using Aleuria aurantia lectin followed by electron transfer dissociation-MS/MS analysis. Most AtSPY targets were nuclear proteins that function in DNA repair, transcription, RNA splicing, and nucleocytoplasmic transport. Cytoplasmic AtSPY targets were involved in microtubule-mediated cell division/growth and protein folding. A comparison with the published O-linked-N-acetylglucosamine (O-GlcNAc) proteome revealed that 30% of AtSPY targets were also O-GlcNAcylated, indicating that these distinct glycosylations could co-regulate many protein functions. This study unveiled the roles of O-fucosylation in modulating many key nuclear and cytoplasmic proteins and provided a valuable resource for elucidating the regulatory mechanisms involved.more » « less
-
Archibald, John (Ed.)Abstract Nuclear matrix constituent proteins in plants function like animal lamins, providing the structural foundation of the nuclear lamina and regulating nuclear organization and morphology. Although they are well characterized in angiosperms, the presence and structure of nuclear matrix constituent proteins in more distantly related species, such as streptophytic algae, are relatively unknown. The rapid evolution of nuclear matrix constituent proteins throughout the plant lineage has caused a divergence in protein sequence that makes similarity-based searches less effective. Structural features are more likely to be conserved compared to primary amino acid sequence; therefore, we developed a filtration protocol to search for diverged nuclear matrix constituent proteins based on four physical characteristics: intrinsically disordered content, isoelectric point, number of amino acids, and the presence of a central coiled-coil domain. By setting parameters to recognize the properties of bona fide nuclear matrix constituent protein proteins in angiosperms, we filtered eight complete proteomes from streptophytic algae species and identified strong nuclear matrix constituent protein candidates in six taxa in the Classes Zygnematophyceae, Charophyceae, and Klebsormidiophyceae. Through analysis of these proteins, we observed structural variance in domain size between nuclear matrix constituent proteins in algae and land plants, as well as a single block of amino acid conservation. Our analysis indicates that nuclear matrix constituent proteins are absent in the Mesostigmatophyceae. The presence versus absence of nuclear matrix constituent protein proteins does not correlate with the distribution of different forms of mitosis (e.g. closed/semi-closed/open) but does correspond to the transition from unicellularity to multicellularity in the streptophytic algae, suggesting that a nuclear matrix constituent protein-based nucleoskeleton plays important roles in supporting cell-to-cell interactions.more » « less
-
The nuclear lamina is an intermediate filament meshwork adjacent to the inner nuclear membrane (INM) that plays a critical role in maintaining nuclear shape and regulating gene expression through chromatin interactions. Studies have demonstrated that A- and B-type lamins, the filamentous proteins that make up the nuclear lamina, form independent but interacting networks. However, whether these lamin subtypes exhibit a distinct spatial organization or whether their organization has any functional consequences is unknown. Using stochastic optical reconstruction microscopy (STORM) our studies reveal that lamin B1 and lamin A/C form concentric but overlapping networks, with lamin B1 forming the outer concentric ring located adjacent to the INM. The more peripheral localization of lamin B1 is mediated by its carboxyl-terminal farnesyl group. Lamin B1 localization is also curvature- and strain-dependent, while the localization of lamin A/C is not. We also show that lamin B1’s outer-facing localization stabilizes nuclear shape by restraining outward protrusions of the lamin A/C network. These two findings, that lamin B1 forms an outer concentric ring and that its localization is energy-dependent, are significant as they suggest a distinct model for the nuclear lamina—one that is able to predict its behavior and clarifies the distinct roles of individual nuclear lamin proteins and the consequences of their perturbation.more » « less
-
Discher, Dennis (Ed.)The LMNA gene encodes the nuclear envelope proteins Lamins A and C, which comprise a major part of the nuclear lamina, provide mechanical support to the nucleus, and participate in diverse-intracellular signaling. LMNA mutations give rise to a collection of diseases called laminopathies, including dilated cardiomyopathy ( LMNA-DCM) and muscular dystrophies. Although nuclear deformities are a hallmark of LMNA-DCM, the role of nuclear abnormalities in the pathogenesis of -DCM remains incompletely understood. Using induced-pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from LMNA-mutant patients and healthy controls, we show that LMNA mutant iPSC-CM nuclei have altered shape or increased size compared with healthy control iPSC-CM nuclei. The LMNA mutation exhibiting the most severe nuclear deformities, R249Q, additionally caused reduced nuclear stiffness and increased nuclear fragility. Importantly, for all cell lines, the degree of nuclear abnormalities corresponded to the degree of Lamin A/C and Lamin B1 mislocalization from the nuclear envelope. The mislocalization was likely due to altered assembly of Lamin A/C. Collectively, these results point to the importance of correct lamin assembly at the nuclear envelope in providing mechanical stability to the nucleus and suggests that defects in nuclear lamina organization may contribute to the nuclear and cellular dysfunction in LMNA-DCM.more » « less
