Induction Of Cell Division Research Articles

Host Responses to Haustorium Invasion of the Stem Parasitic Plant, Cuscuta campestris, Differ from Responses to Wounding.

The parasitic mechanism employed by the stem parasitic plant, Cuscuta campestris, involves degradation of the host epidermis and intrusion of the cortical tissue of the host stem by a specialized organ called the haustorium. In host plants, the mechanical stimuli associated with this degradation and intrusion of host tissues is considered to be comparable to wounding. However, it has not yet been clarified whether parasitic invasion and wounding induce equivalent responses in host plants. In this study, we demonstrated that parasitic intrusion induced responses that were comparable to wounding in the host plant, Arabidopsis thaliana, including up-regulation of Arabidopsis NAC DOMAIN-CONTAINING PROTEIN 71 (ANAC071), which is a key transcription factor associated with wound repair, cell division, and vascular development. Despite these similarities, we found that the mechanism regulating the induction of cell division- and vascular development-related genes at the host-parasite interface differed from that associated with wound repair. Specifically, ANAC071 was not required for the induction of cell division-related genes, as their upregulation was observed in anac071/096/011 triple mutants as well as in wild-type host plants. We also found that neither auxin nor ethylene plays a significant role in inducing the expression of vascular development-related genes. Thus, the findings show that the mechanisms responsible for upregulating cell division- and vascular development-related genes differ between parasitic and wound repair responses.

Apoptotic extracellular vesicles carrying Mif regulate macrophage recruitment and compensatory proliferation in neighboring epithelial stem cells during tissue maintenance.

Apoptotic cells can signal to neighboring cells to stimulate proliferation and compensate for cell loss to maintain tissue homeostasis. While apoptotic cell-derived extracellular vesicles (AEVs) can transmit instructional cues to mediate communication with neighboring cells, the molecular mechanisms that induce cell division are not well understood. Here, we show that macrophage migration inhibitory factor (Mif)-containing AEVs regulate compensatory proliferation via ERK signaling in epithelial stem cells of larval zebrafish. Time-lapse imaging showed efferocytosis of AEVs from dying epithelial stem cells by healthy neighboring stem cells. Proteomic and ultrastructure analysis of purified AEVs identified Mif localization on the AEV surface. Pharmacological inhibition or genetic mutation of Mif, or its cognate receptor CD74, decreased levels of phosphorylated ERK and compensatory proliferation in the neighboring epithelial stem cells. Disruption of Mif activity also caused decreased numbers of macrophages patrolling near AEVs, while depletion of the macrophage lineage resulted in a reduced proliferative response by the epithelial stem cells. We propose that AEVs carrying Mif directly stimulate epithelial stem cell repopulation and guide macrophages to cell non-autonomously induce localized proliferation to sustain overall cell numbers during tissue maintenance.

Physiological Indexes in Seed Germination and Seedling Growth of Rangpur Lime (Citrus limonia L. Osbeck) under Plant Growth Regulators

The propagation of citrus seedlings is accomplished through grafting, utilizing seeds for the production of rootstocks. The germination of certain seeds may be low and uneven, complicating the production of high-quality seedlings. The use of plant growth regulators (PGRs) is a viable alternative to improve the quality of seedling production, as these compounds can break dormancy, control the hydrolysis of reserves, induce cell division, and regulate permeability and protein functions. This study aimed to evaluate the germination of seeds and the growth of Rangpur lime (Citrus limonia L. Osbeck) seedlings under the influence of imbibition in solutions of gibberellic acid (GA3) and a combination of GA4+7 + 6Benzyladenine. The experiment was conducted under controlled laboratory and greenhouse conditions, using a completely randomized design in a 2 × 5 factorial scheme, with two types of plant regulators (GA3 and GA4+7 + 6BA) at five concentrations (0, 250, 500, 750, and 1000 mg L−1 a.i.). Quantitative and qualitative variables were evaluated, ranging from seed germination to seedling development and formation, including germination percentage and speed index, fresh and dry biomass of roots and shoots, enzymatic activity, and gas exchange. The results indicate that GA3 significantly accelerates the germination process of Rangpur lime cv. Santa Cruz seeds and promotes better seedling growth and development, resulting in vigorous seedlings. These findings demonstrate that the application of PGRs, particularly GA3, can substantially enhance the propagation efficiency of citrus rootstocks, offering a practical solution for improving the uniformity and quality of seedling production in commercial settings.

Molecular Dynamics Simulations Show That Short Peptides Can Drive Synthetic Cell Division by Binding to the Inner Membrane Leaflet.

An important functionality of lifelike "synthetic cells" is to mimic cell division. Currently, specialized proteins that induce membrane fission in living cells are the primary candidates for dividing synthetic cells. However, interactions between lipid membranes and proteins that are not found in living cells may also be suitable. Here, we discuss the potential of short membrane-anchored peptides to induce cell division. Specifically, we used the coarse-grained MARTINI model to investigate the interaction between short membrane-anchored peptides and a lipid bilayer patch. The simulation revealed that the anchored peptide induces significant spontaneous curvature and suggests that the lipid-peptide complex can be considered as a conically shaped "bulky headgroup" lipid. By systematically increasing the electrostatic charge of the peptide, we find that membrane-anchored peptides may generate sufficiently large constriction forces even at dilute coverages. Finally, we show that when the peptide has an opposite charge to the membrane, the peptide may induce division by binding the inner membrane leaflet of a synthetic cell, that is, cell division from within.

Abstract We019: YAP Overcomes Mechanical Barriers to Induce Adult Cardiomyocyte Division

Adult mammalian cardiomyocytes (CMs) are among the least able to renew of all cell types. CMs exit the cell cycle soon after birth and remain cell cycle arrested by unknown mechanisms. We previously found that in adult CMs, the active form of the Hippo signaling pathway effector YAP, YAP5SA, induces cell division in vivo . Here, we analyze the mechanism by which YAP5SA regulates the cell cycle in adult CMs. YAP5SA-expressing adult CMs reenter the cell cycle at the G1/S transition and have a prolonged S-phase lasting approximately 48 hours. Molecular and functional analysis revealed that progression from S to G2 phase, and the induction of mitotic rounding, requires sarcomere disassembly. Transition from G2 to M phase requires overcoming DNA damage checkpoint facilitated by the activation of the P21 degradation pathway. Clonal analysis showed that approximately 20% of CMs progress through cytokinesis. Our results show that multiple barriers are involved in suppressing the adult CM cell cycle. These include the structural block caused by the highly structured CM cytoskeleton and the P21 regulated DNA damage checkpoint.

Functional characterization of D-type cyclins involved in cell division in rice

BackgroundD-type cyclins (CYCD) regulate the cell cycle G1/S transition and are thus closely involved in cell cycle progression. However, little is known about their functions in rice.ResultsWe identified 14 CYCD genes in the rice genome and confirmed the presence of characteristic cyclin domains in each. The expression of the OsCYCD genes in different tissues was investigated. Most OsCYCD genes were expressed at least in one of the analyzed tissues, with varying degrees of expression. Ten OsCYCD proteins could interact with both retinoblastoma-related protein (RBR) and A-type cyclin-dependent kinases (CDKA) forming holistic complexes, while OsCYCD3;1, OsCYCD6;1, and OsCYCD7;1 bound only one component, and OsCYCD4;2 bound to neither protein. Interestingly, all OsCYCD genes except OsCYCD7;1, were able to induce tobacco pavement cells to re-enter mitosis with different efficiencies. Transgenic rice plants overexpressing OsCYCD2;2, OsCYCD6;1, and OsCYCD7;1 (which induced cell division in tobacco with high-, low-, and zero-efficiency, respectively) were created. Higher levels of cell division were observed in both the stomatal lineage and epidermal cells of the OsCYCD2;2- and OsCYCD6;1-overexpressing plants, with lower levels seen in OsCYCD7;1-overexpressing plants.ConclusionsThe distinct expression patterns and varying effects on the cell cycle suggest different functions for the various OsCYCD proteins. Our findings will enhance understanding of the CYCD family in rice and provide a preliminary foundation for the future functional verification of these genes.

Gibberellin acid 4 and 7 increase indole-3-acetic acid production and induce cell division via PbCRF4-mediated activation of PbYUCCA6 expression in ‘Dangshansu’ pear

The role of gibberellins in inducing cell division is now widely recognized; however, the underlying mechanisms remain to be clarified. Here, we demonstrate that gibberellin acid 4 and 7 (GA4+7) can induce active cell division leading to ovary expansion as CPPU (N-(2‑chloro-4-pyridyl)-N’-phenylurea) at the early fruit setting stage in ‘Dangshansu’ pear (Pyrus bretshneideri Rehd.). Transcriptomic analysis showed PbCYTOKININ RESPONSE FACTOR4 (PbCRF4) was activated in response to GA4+7 and CPPU, suggesting a candidate gene correlated to gibberellin-induced cell division during early fruit development. Overexpression and RNA interference of PbCRF4 in pear calli demonstrated a role of PbCRF4 in regulating fruit cell proliferation and increased indole-3-acetic acid (IAA) biosynthesis. Ectopic overexpression of PbCRF4 in tomato produced flat fruits with no pointed tips, decreased the fruit index, and increased the pericarp thickness and IAA content. Silencing of SlCRF4 in tomato led to pointed-tip fruits with a relatively low IAA content and reduced pericarp thickness. Furthermore, PbCRF4 transcriptionally activated indole-3-pyruvate monooxygenase 6 (YUCCA6) to increase IAA content in pear. Taken together, this study reveals that GA4+7 induces cell division and an increase in IAA content via regulating PbCRF4 to activate the expression of PbYUCCA6, thereby contributing to the control of fruit shape.

A novel small molecule inhibitor of p38⍺ MAP kinase augments cardiomyocyte cell cycle entry in response to direct cell cycle stimulation.

Myocardial infarction (MI) is the leading cause of mortality globally due in part to the limited ability of cardiomyocytes (CMs) to regenerate. Recently, we demonstrated that overexpression of four-cell cycle factors, CDK1, CDK4, cyclin B1 and cyclin D1 (4F), induced cell division in ~20% of the post-mitotic CMs overexpressed 4F. The current study aims to identify a small molecule that augments 4F-induced CM cycle induction. Screening of small molecules with a potential to augment 4F-induced cell-cycle induction in 60-day-old mature human induced pluripotent cardiomyocytes (hiPS-CMs) revealed N-(4,6-Dimethylpyridin-2-yl)-4-(pyridine-4-yl)piperazine-1-carbothioamide (NDPPC), which activates cell cycle progression in 4F-transduced hiPS-CMs. Autodock tool and Autodock vina computational methods showed that NDPPC has a potential interaction with the binding site at the human p38⍺ mitogen-activated protein kinase (p38⍺ MAP kinase), a critical negative regulator of the mammalian cell cycle. A p38 MAP kinase activity assay showed that NDPPC inhibits p38⍺ with 5-10 times lower IC50 compared to the other P38 isoforms in a dose-dependent manner. Overexpression of p38⍺ MAP kinase in CMs inhibited 4F cell cycle induction, and treatment with NDPPC reversed the cell cycle inhibitory effect. NDPPC is a novel inhibitor for p38 MAP kinase and is a promising drug to augment CM cell cycle response to the 4F. NDPPC could become an adjunct treatment with other cell cycle activators for heart failure treatment.

Effect of glucose on germination performance in two soybean cultivars

Glucose promotes increases in physiological processes related to plant growth and induces cell division and can also act in seed germination. The present investigation has been carried out on the influence of various concentrations of glucose on the germination performance of soybeans seeds of cv. BMX and 66i68. Seeds of soybeans (Glycine max (L.) Merrill) were treated with three concentrations of the glucose (0.05, 0.10 and 0.20 mmol L-1), and a control with distilled water. Tests of seed germination and vigor were carried out: it was calculated the germination percentage (first and final counting), percentage of normal seedlings; and speed of germination, length of the primary root and the aerial part of seedlings were recorded. The experiment was arranged in a completely randomized design with three treatments and five repetitions depending on the test. Increasing doses of the plant growth regulator influence the germination and can increase the speed of germination. The use of glucose in the treatment of soybean seeds, increases the rate of germination and emergence speed, growth of the root system and medium of seedlings. Soybean cultivar BMX seeds showed an increase in physiological performance with increasing glucose dosage.

Deeper inside, the use of chitooligosaccharides, in wound healing process: A computational approach

Chitooligosaccharides (COs) containing up to 10 monomeric units of N-acetyl D-glucosamine and/or D-glucosamine are water-soluble molecules revealing numerous biological activities and low toxicological profiles. Within this study, a computational approach has been used to predict the involvement of the COs having distinct chemical properties (molecular weight, deacetylation degree and acetylation pattern) in all the four wound healing phases: hemostasis, inflammation, proliferation and tissue remodeling. There are predictions, for the investigated COs, regarding their molecular targets and the biological activities that are reliant to the wound healing process. Furthermore, a molecular docking approach was used to assess the interactions of the investigated COs with the myeloid differentiation factor 2 (MD-2), a protein involved in the inflammatory processes. The investigation confirms the functional roles of the investigated COs in wound healing. The molecular targets predicted for the COs containing totally and partially acetylated units are galectins and selectins and those predicted for COs containing totally deacetylated units are fibroblast growing factors, the COs containing 3 units revealing the higher number of molecular targets. All these proteins are involved in mediating immune response, inducing cell division, growth and cell adhesion during the process of wound healing. All the COs containing from 2 to 8 monomeric units are able to interact with the MD-2 protein, the interactions being stronger for the COs containing 6 and 8 monomeric units. The interaction energies increase with the increasing molecular weight and with decreasing deacetylation degree and are reliant on acetylation patterns. Among the investigated COs, the totally acetylated COs containing 6 and 8 N-acetyl glucosamine units can be better inhibitors of the LPS binding to MD-2 protein. Consequently, mixtures of COs with distinct properties should be considered suitable candidates as adjuvants in developing scaffolds for the wound healing process.

Ontogenes and Their Role in Cellular Construction

The genes referred to as ontogenes are responsible for conditional mutations. Based on the results of the research of conditional mutations in D. melanogaster, we attempt to figure out the biological role of ontogenes. We conclude that ontogenes in the process of individual development control the construction of the living organisms of cells (cellular construction), which comprises the induction of cell division, determination of division plane, and the location of daughter cells after the division is completed. The process of morphogenesis consists of cellular construction and protein synthesis. Protein synthesis is controlled by protein-coding (Mendelian) genes. Mendelian genes are switched on by ontogenes. In terms of the two-component genome composed of Mendelian genes and ontogenes, we consider 1) the concept of biological character; 2) interspecific incompatibility; 3) ontogenesis; 4) phylogenesis; and 5) mutagenesis. Ontogenes, which control cellular construction, possess the specific features unusual for Mendelian genes, namely, 1) the activity in germ line tissue; 2) remote interaction; and 3) activity in a compacted state (heterochromatization). These specific features of ontogenes suggest that unlike the Mendelian genes with their chemical activity, ontogenes possess another type of activity (biophysical) involving induction of an electromagnetic field.

Confocal Microscopic Assays of Mitotically Active Proteins in an Agrobacterial Infiltration-Based, Cell Division-Enabled Leaf System of Tobacco (Nicotiana benthamiana).

The production of tissues and organs in plants is brought about by mitotic cell divisions, starting from the zygote. Successful mitosis and cytokinesis harness the functional input of proteins that are expressed in cell cycle-dependent manners to regulate cytoskeletal reorganization and intracellular motility. Fluorescence microscopic assays of mitotically active proteins have been dependent on time-consuming transformation experiments in a host plant or cultured cells. To facilitate the detection and observation of cell cycle-dependent localization and dynamics of plant proteins, we demonstrate, in this chapter, a transiently induced cell division system in Nicotiana benthamiana, named the cell division-enabled leaf system (CDELS). Plasmid constructs which express the D-type cyclin along with a fluorescent fusion protein(s) of interestare delivered to the leaves of N. benthamiana by agrobacterial infiltration. Ectopic expression of cyclin D induces leaf epidermal cells to re-enter mitosis and subsequently cytokinesis, allowing the dynamic localization of fluorescent fusion protein(s) to be observed throughout the course of mitotic cell division using live-cell fluorescence microscopy. This effective approach not only allows one to detect mitotic activities of novel proteins but also record their dynamics and relationship with others during mitosis and cytokinesis in a greatly shortened period of time.

A novel type of phytosulfokine, PSK-ε, positively regulates root elongation and formation of lateral roots and root nodules in Medicago truncatula

ABSTRACT Phytosulfokines (PSKs) are a class of tyrosine-sulfated pentapeptides. PSK-α, PSK-γ, and PSK-δ are three reported PSK members involved in regulating plant growth, development, and resistance to biotic and abiotic stresses. Here, we reported a novel type of PSK, PSK-ε with the sequence YSO3VYSO3TN, and its precursor proteins (MtPSKε, LjPSKε, and GmPSKε), specifically from legume species. PSK-ε peptide differs from PSK-δ by one amino acid and is close to PSK-δ in the phylogenetic relationship. Expression profile analysis showed that MtPSKε was highly expressed in Medicago truncatula roots, especially in root tips and emerged lateral roots. Application of the synthetic sulfated PSK-ε peptide and overexpression of MtPSKε significantly promoted M. truncatula root elongation and increased lateral root number, probably by inducing cell division and expansion in roots. Furthermore, MtPSKε expression was induced by rhizobia infection and was detected in root nodules including nodule primordia. Both PSK-ε peptide treatment and MtPSKε overexpression significantly increased nodule number in M. truncatula. Taken together, these results demonstrate that PSK-ε, a novel type of phytosulfokine, positively regulates root elongation and formation of lateral root and root nodule in M. truncatula.

Understanding the mechanisms of HPV-related carcinogenesis: Implications for cell cycle dynamics

The role of human papillomavirus (HPV) as a causative agent for epithelial cancers is well-known, but many open questions remain regarding the downstream gene regulatory effects of viral proteins E6 and E7 on the cell cycle. Here, we extend a cell cycle model originally presented by Gérard and Goldbeter (2009) in order to capture the effects of E6 and E7 on key actors in the cell cycle. Results suggest that E6 is sufficient to reverse p53-induced quiescence, while E7 is sufficient to reverse p16INK4a-induced quiescence; both E6 and E7 are necessary when p53 and p16INK4a are both active. Moreover, E7 appears to play a role as a “growth factor substitute”, inducing cell division in the absence of growth factor. Low levels of E7 may permit regular cell division, but the results suggest that higher levels of E7 dysregulate the cell cycle in ways that may destabilize the cellular genome. The mechanisms explored here provide opportunities for developing new treatment targets that take advantage of the cell cycle regulatory system to prevent HPV-related cancer effects.

Abstract P1029: Improving Cardiomyocyte Cell Cycle Entry In Response To Direct Cell Cycle Stimulation Using A Novel Small Molecule Inhibitor Of P38

Background: Myocardial infarction is the leading cause of mortality globally, due in part to the limited ability of cardiomyocytes (CMs) to regenerate. Recently, we showed that overexpression of a combination of 4 cell cycle factors, CDK1, CDK4, cyclin B1, and cyclin D1 (collectively known as 4F), induced cell division in ~15% of post-mitotic mouse, rat, and human CMs. The aim of the current study is to identify novel small molecules that further augment CM cycle induction caused by the 4F. Methods and Results: We performed a drug screening of 30 chemical compounds with possible cell cycle regulatory activities using 60-day-old mature hiPS-CMs overexpressing the 4F and assessed the increase in EDU (DNA synthesis marker) and PHH3 (G2-M phase marker). The top hit was N-(4,6-Dimethylpyridin-2-yl)-4-(pyridin-4-yl)piperazine-1-carbothioamide (NDPPC). NDPPC showed a dose-dependent increase in the percentage of EDU and PHH3 positive nuclei in hiPS-CMs transduced with 4F. CMs transduced with 4F and treated with 1 μM NDPPC showed a significant increase in the percentage of EDU and PHH3 compared with vehicle (V)-treated CMs (PHH3; V: 20.41±2.02%, NDPPC: 33.75±3.9%, EDU; V: 18.24±1.7%, NDPPC: 30.81±2.1% n=6, p<0.001). In Silico Drug-Target prediction showed that NDPPC could interact with p38 mitogen-activated protein kinase (P38), a critical negative regulator of mammalian cell cycle. Therefore, we overexpressed P38, in the presence and absence of NDPPC and 4F. As expected, overexpression of P38 in CMs inhibited 4F cell cycle induction, and treatment with NDPPC reversed the cell cycle inhibitory effect (in presence of 4F PHH3%; V: 20.38±0.97%, P38 overexpression+V: 11.02±1.3%, P38 overexpression+NDPPC: 23.62±2.79, n=4, P<0.001). Knockdown of P38 showed a significant increase in the percentage of EDU and PHH3 positive nuclei in 4F treated CMs, and treatment with NDPPC did not show any further increase in cell cycle induction. These data indicate that NDPPC enhances the 4F cell cycle response in CMs through inhibition of P38. Conclusions: NDPPC is a novel inhibitor for P38. NDPPC is a promising drug to promote CM cell cycle response to the 4F. Further work in vivo is needed to test whether NDPPC could improve the 4F effect on cardiac function after ischemic injury.

Visualization of individual cell division history in complex tissues using iCOUNT.

SummaryThe division potential of individual stem cells and the molecular consequences of successive rounds of proliferation remain largely unknown. Here, we developed an inducible cell division counter (iCOUNT) that reports cell division events in human and mouse tissues in vitro and in vivo. Analyzing cell division histories of neural stem/progenitor cells (NSPCs) in the developing and adult brain, we show that iCOUNT can provide novel insights into stem cell behavior. Further, we use single-cell RNA sequencing (scRNA-seq) of iCOUNT-labeled NSPCs and their progenies from the developing mouse cortex and forebrain-regionalized human organoids to identify functionally relevant molecular pathways that are commonly regulated between mouse and human cells, depending on individual cell division histories. Thus, we developed a tool to characterize the molecular consequences of repeated cell divisions of stem cells that allows an analysis of the cellular principles underlying tissue formation, homeostasis, and repair.

Armeniaspirols inhibit the AAA+ proteases ClpXP and ClpYQ leading to cell division arrest in Gram-positive bacteria

Multi-drug-resistant bacteria present an urgent threat to modern medicine, creating a desperate need for antibiotics with new modes of action. As natural products remain an unsurpassed source for clinically viable antibiotic compounds, we investigate the mechanism of action of armeniaspirol. The armeniaspirols are a structurally unique class of Gram-positive antibiotic discovered from Streptomyces armeniacus for which resistance cannot be readily obtained. We show that armeniaspirol inhibits the ATP-dependent proteases ClpXP and ClpYQ invitro and in the model Gram-positive Bacillus subtilis. This inhibition dysregulates the divisome and elongasome supported by an upregulation of key proteins FtsZ, DivIVA, and MreB inducing cell division arrest. The inhibition of ClpXP and ClpYQ to dysregulate cell division represents a unique antibiotic mechanism of action and armeniaspirol is the only known natural product inhibitor of the coveted anti-virulence target ClpP. Thus, armeniaspirol possesses a promising lead scaffold for antibiotic development with unique pharmacology.

GA3 is superior to GA4 in promoting bud endodormancy release in tree peony (Paeonia suffruticosa) and their potential working mechanism

BackgroundSufficient low temperature accumulation is the key strategy to break bud dormancy and promote subsequent flowering in tree peony anti-season culturing production. Exogenous gibberellins (GAs) could partially replace chilling to accelerate dormancy release, and different kinds of GAs showed inconsistent effects in various plants. To understand the effects of exogenous GA3 and GA4 on dormancy release and subsequent growth, the morphological changes were observed after exogenous GAs applications, the differentially expressed genes (DEGs) were identified, and the contents of endogenous phytohormones, starch and sugar were measured, respectively.ResultsMorphological observation and photosynthesis measurements indicated that both GA3 and GA4 applications accelerated bud dormancy release, but GA3 feeding induced faster bud burst, higher shoot and more flowers per plant. Full-length transcriptome of dormant bud was used as the reference genome. Totally 124 110 459, 124 015 148 and 126 239 836 reads by illumina transcriptome sequencing were obtained in mock, GA3 and GA4 groups, respectively. Compared with the mock, there were 879 DEGs and 2 595 DEGs in GA3 and GA4 group, 1 179 DEGs in GA3 vs GA4, and 849 DEGs were common in these comparison groups. The significant enrichment KEGG pathways of 849 DEGs highlighted plant hormone signal transduction, starch and sucrose metabolism, cell cycle, DNA replication, etc. Interestingly, the contents of endogenous GA1, GA3, GA4, GA7 and IAA significantly increased, ABA decreased after GA3 and GA4 treatments by LC–MS/MS. Additionally, the soluble glucose, fructose and trehalose increased after exogenous GAs applications. Compared to GA4 treatment, GA3 induced higher GA1, GA3 and IAA level, more starch degradation to generate more monosaccharide for use, and promoted cell cycle and photosynthesis. Higher expression levels of dormancy-related genes, TFL, FT, EBB1, EBB3 and CYCD, and lower of SVP by GA3 treatment implied more efficiency of GA3.ConclusionsExogenous GA3 and GA4 significantly accelerated bud dormancy release and subsequent growth by increasing the contents of endogenous bioactive GAs, IAA, and soluble glucose such as fructose and trehalose, and accelerated cell cycle process, accompanied by decreasing ABA contents. GA3 was superior to GA4 in tree peony forcing culture, which might because tree peony was more sensitive to GA3 than GA4, and GA3 had a more effective ability to induce cell division and starch hydrolysis. These results provided the value data for understanding the mechanism of dormancy release in tree peony.

Induction of cell division and antioxidative enzyme activity of Matricaria chamomilla L. cell line under clino-rotation

This study represents an optimized protocol for cell line culture of Matricaria chamomilla and the impact of clino-rotation on cell division, cell growth, and antioxidant enzyme activities for the first time. The cell suspension was transferred in the solid MS medium supplied with 2, 4-D, and KIN. Then the calli produced from a cell line were selected for callus subculture and clino-rotation treatment for 7 days by a 2D-clinostat. A significant rise of fresh and dry weights, cell division, total soluble sugar, reducing sugar, and starch contents were detected under clino-rotation. Protein content approximately unchanged in microgravity-treated calli. Antioxidant enzymes activities, such as peroxidase, catalase (CAT), and superoxide dismutase were elevated in calli exposed to microgravity. CAT activity showed a more than three-fold increase than that of control. According to native polyacrylamide gel electrophoresis, all the antioxidant enzymes isoforms were stronger in clino-rotated calli than that of the untreated control. Microgravity also stimulated H2O2 production and markedly adjusted lipid peroxidation in calli exposed to clino-rotation. These findings suggest that clino-rotation with stimulation of carbohydrate accumulation and antioxidant enzymes mitigates oxidative stress and improves growth and cell division. The isolation of M. chamomilla cell line with high growth was conducted to study the impact of clino-rotation on some cellular and antioxidative enzyme responses. Clino-rotation stimulated the cell division and growth by induction of antioxidant enzyme activities.

Abstract 278: Metabolic Reprogramming is Essential for Cell Cycle Progression in Cardiomyocytes

Myocardial infarction causes irreversible loss of cardiomyocytes (CMs) and often leads to heart failure. To replace the lost cells, we identified a combination of cell-cycle regulators that induces stable cytokinesis in adult post-mitotic cells. Specifically, adenoviral overexpression of cyclin-dependent kinase 1 (CDK1), CDK4, cyclin B1, and cyclin D1 (collectively known as ‘four factors’, or simply 4F) induced cell division in ~15% of post-mitotic mouse, rat, and human CMs. Identifying the major roadblocks during the process of CM proliferation is a key for advancing this field. This was not possible before due to the lack of efficient methods to induce CM proliferation. The goal of the current study is to understand why a subpopulation of CMs divide while most CMs, despite expressing 4F, resist cell cycle reentry. To investigate transcriptional changes during cell cycle progression at the single cell level, we conducted temporal single cell RNAseq on 60-day-old matured hiPS-CMs infected with either LacZ (control) or 4F for 24, 48 and 72 h. We found a unique cell population that appears 48 h after infection with the 4F; this population was identified as the proliferating population and expressed high levels of cytokinesis genes (Ki67, Aurora Kinase A and B, E2F1, CDC20, ANLN, TK1, CCNA2, PLK1 and PCNA). Consistent with our published data, this population represents ~15% of the total CMs population expressing 4F. Compared with the quiescent population from the same sample, this unique population of proliferating CMs shows significant upregulation of the cell cycle program and major downregulation of mitochondrial electron transport chain genes. In line with these transcriptomic changes, hiPS-CMs had 50% lower rates of oxidative phosphorylation 48 h after 4F infection. Furthermore, in 4F-overexpressing iPS-CMs, stable isotope tracing demonstrated significantly higher enrichment of glucose-derived 13 C in NAD and UDP-HexNAc, suggesting activation of NAD synthesis and the hexosamine biosynthetic pathway. We conclude that proliferating CMs diminish catabolic pathway activity and augment biosynthetic pathway activity. The capacity of CM subpopulation to reprogram their metabolism is likely to facilitate their ability to complete cell division.