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BUALUANG FAIYUE MOHAMMED J. AL‐AZZAWI TIMOTHY J. FLOWERS 《Plant, cell & environment》2010,33(5):702-716
Although an apoplastic pathway (the so‐called bypass flow) is implicated in the uptake of Na+ by rice growing in saline conditions, the point of entry of this flow into roots remains to be elucidated. We investigated the role of lateral roots in bypass flow using the tracer trisodium‐8‐hydroxy‐1,3,6‐pyrenetrisulphonic acid (PTS) and the rice cv. IR36. PTS was identified in the vascular tissue of lateral roots using both epifluorescence microscopy and confocal laser scanning microscopy. Cryo‐scanning electron microscopy and epifluorescence microscopy of sections stained with berberine‐aniline blue revealed that the exodermis is absent in the lateral roots. We conclude that PTS can move freely through the cortical layers of lateral roots, enter the stele and be transported to the shoot via the transpiration stream. 相似文献
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Cytokinesis is the last step of the M (mitosis) phase, yet it is crucial for the faithful division of one cell into two. Cytokinesis failure is often associated with cancer. Cytokinesis can be morphologically divided into four steps: cleavage furrow initiation, cleavage furrow ingression, midbody formation and abscission. Molecular studies have revealed that RhoA as well as its regulators and effectors are important players to ensure a successful cytokinesis. At the same time, Polo-like kinase 1 (Plk1) is an important kinase that can target many substrates and carry out different functions during mitosis, including cytokinesis. Recent studies are beginning to unveil a closer tie between Plk1 and RhoA networks. More specifically, Plk1 phosphorylates the centralspindlin complex Cyk4 and MKLP1/CHO1, thus recruiting RhoA guanine nucleotide-exchange factor (GEF) Ect2 through its phosphopeptide-binding BRCT domains. Ect2 itself can be phosphorylated by Plk1 in vitro. Plk1 can also phosphorylate another GEF MyoGEF to regulate RhoA activity. Once activated, RhoA-GTP will activate downstream effectors, including ROCK1 and ROCK2. ROCK2 is among the proteins that associate with Plk1 Polo-binding domain (PBD) in a large proteomic screen, and Plk1 can phosphorylate ROCK2 in vitro. We review current understandings of the interplay between Plk1, RhoA proteins and other proteins (e.g., NudC, MKLP2, PRC1, CEP55) involved in cytokinesis, with particular emphasis of its clinical implications in cancer. 相似文献
54.
Cytokinesis is the last step of the M (mitosis) phase,yet it is crucial for the faithful division of one cell into two.Cytokinesis failure is often associated with cancer.Cytokinesis can be morphologically divided into four steps:cleavage furrow initiation,cleavage furrow ingression,midbody formation and abscission.Molecular studies have revealed that RhoA as well as its regulators and effectors are important players to ensure a successful cytokinesis.At the same time,Polo-like kinase 1 (Plk1) is an important kinase that can target many substrates and carry out different functions during mitosis,including cytokinesis.Recent studies are beginning to unveil a closer tie between Plk1 and RhoA networks.More specifically,Plk1 phosphorylates the centralspindlin complex Cyk4 and MKLP1/CHO1,thus recruiting RhoA guanine nucleotide-exchange factor (GEF) Ect2 through its phosphopeptide-binding BRCT domains.Ect2 itself can be phosphorylated by Plk1 in vitro.Plk1 can also phosphorylate another GEF MyoGEF to regulate RhoA activity.Once activated,RhoA-GTP will activate downstream effectors,including ROCK1 and ROCK2.ROCK2 is among the proteins that associate with Plk1 Polo-binding domain (PBD) in a large proteomic screen,and Plk1 can phosphorylate ROCK2 in vitro.We review current understandings of the interplay between Plk1,RhoA proteins and other proteins (e.g.,NudC,MKLP2,PRC1,CEP55) involved in cytokinesis,with partitular emphasis of its clinical implications in cancer. 相似文献
55.
DNA replication is highly regulated in most organisms. Although much research has focused on mechanisms that regulate initiation of replication, mechanisms that regulate elongation of replication are less well understood. We characterized a mechanism that regulates replication elongation in the bacterium Bacillus subtilis. Replication elongation was inhibited within minutes after amino acid starvation, regardless of where the replication forks were located on the chromosome. We found that small nucleotides ppGpp and pppGpp, which are induced upon starvation, appeared to inhibit replication directly by inhibiting primase, an essential component of the replication machinery. The replication forks arrested with (p)ppGpp did not recruit the recombination protein RecA, indicating that the forks are not disrupted. (p)ppGpp appear to be part of a surveillance mechanism that links nutrient availability to replication by rapidly inhibiting replication in starved cells, thereby preventing replication-fork disruption. This control may be important for cells to maintain genomic integrity. 相似文献
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Wang BJ Cui ZJ 《American journal of physiology. Regulatory, integrative and comparative physiology》2007,292(2):R666-R678
The field of cholecystokinin (CCK) stimulation of exocrine pancreatic secretion has experienced major changes in the recent past. This review attempts to summarize the present status of the field. CCK production in the intestinal I cells, the molecular forms of CCK produced and subsequently circulated in the blood, the presence or absence of CCK receptors on the isolated pancreatic acinar cells and the associated signaling for acinar cell secretion, and the actual circuits and sites of action for CCK regulation of exocrine pancreatic secretion in vivo are reviewed in different animal species with an emphasis on birds, rodents, and humans. Clear differences in the relative importance of neural and direct modes of CCK action on pancreatic acinar cells were identified. Rodents seem to be endowed with both modes of action, whereas in humans the neural mode may predominate. In birds, such as duck, the direct mode needs further assistance from pituitary adenylate cyclase-activating peptide/VIP receptors. However, much further work needs to be directed to the neural mode to map out all sites of CCK action and details of the full circuits, and we foresee a major revival for this field of research in the near future. 相似文献
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Kyle Lapham Mark N. Kvale Jue Lin Sheryl Connell Lisa A. Croen Brad P. Dispensa Lynn Fang Stephanie Hesselson Thomas J. Hoffmann Carlos Iribarren Eric Jorgenson Lawrence H. Kushi Dana Ludwig Tetsuya Matsuguchi William B. McGuire Sunita Miles Charles P. Quesenberry Jr. Sarah Rowell Marianne Sadler Lori C. Sakoda David Smethurst Carol P. Somkin Stephen K. Van Den Eeden Lawrence Walter Rachel A. Whitmer Pui-Yan Kwok Neil Risch Catherine Schaefer Elizabeth H. Blackburn 《Genetics》2015,200(4):1061-1072
The Kaiser Permanente Research Program on Genes, Environment, and Health (RPGEH) Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort includes DNA specimens extracted from saliva samples of 110,266 individuals. Because of its relationship to aging, telomere length measurement was considered an important biomarker to develop on these subjects. To assay relative telomere length (TL) on this large cohort over a short time period, we created a novel high throughput robotic system for TL analysis and informatics. Samples were run in triplicate, along with control samples, in a randomized design. As part of quality control, we determined the within-sample variability and employed thresholds for the elimination of outlying measurements. Of 106,902 samples assayed, 105,539 (98.7%) passed all quality control (QC) measures. As expected, TL in general showed a decline with age and a sex difference. While telomeres showed a negative correlation with age up to 75 years, in those older than 75 years, age positively correlated with longer telomeres, indicative of an association of longer telomeres with more years of survival in those older than 75. Furthermore, while females in general had longer telomeres than males, this difference was significant only for those older than age 50. An additional novel finding was that the variance of TL between individuals increased with age. This study establishes reliable assay and analysis methodologies for measurement of TL in large, population-based human studies. The GERA cohort represents the largest currently available such resource, linked to comprehensive electronic health and genotype data for analysis. 相似文献