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Peter W. Barlow 《Plant and Soil》1994,167(1):1-16
The summit of roots of various plant species may be occupied by a single, rapidly proliferating tetrahedral apical cell (as in ferns), or by a multicellular and slowly proliferating quiescent centre (as in angiosperms), or by intermediate types of cellular organizations. The present paper attempts to deduce the phylogeny of these various types of cellular patterning at the root apex. 相似文献
3.
Somatic stem/progenitor cells actively proliferate and give rise to different types of mature cells (active state) in embryonic tissues while they are mostly dormant (quiescent state) in many adult tissues. Notch signaling is known to regulate both active and quiescent states of somatic stem cells, but how it regulates these different states is unknown. Recent studies revealed that the Notch effector Hes1 is expressed differently during the active and quiescent states during neurogenesis and myogenesis: high in the quiescent state and oscillatory in the active state. When the Hes1 expression level is high, both Ascl1 and MyoD expression are continuously suppressed. By contrast, when Hes1 expression oscillates, it periodically represses expression of the neurogenic factor Ascl1 and the myogenic factor MyoD, thereby driving Ascl1 and MyoD oscillations. High levels of Hes1 and the resultant Ascl1 suppression promote the quiescent state of neural stem cells, while Hes1 oscillation-dependent Ascl1 oscillations regulate their active state. Similarly, in satellite cells of muscles, known adult muscle stem cells, high levels of Hes1 and the resultant MyoD suppression seem to promote their quiescent state, while Hes1 oscillation-dependent MyoD oscillations activate their proliferation and differentiation. Therefore, the expression dynamics of Hes1 is a key regulatory mechanism of generating and maintaining active/quiescent stem cell states. 相似文献
4.
Tom Denyer Xiaoli Ma Simon Klesen Emanuele Scacchi Kay Nieselt Marja C.P. Timmermans 《Developmental cell》2019,48(6):840-852.e5
5.
Instability in the root meristem of Zea mays L. during growth 总被引:1,自引:1,他引:0
6.
Keiko Oku 《Journal of Ethology》2009,27(2):279-283
In the Kanzawa spider mite, Tetranychus kanzawai (Acari: Tetranychidae), adult males guard pre-reproductive quiescent females. I experimentally examined the effects of density
experience during development and/or after adult emergence on precopulatory mate guarding behavior by T. kanzawai males. Mate guarding behavior was modified by density experience after adult emergence. When males had previously experienced
high density after adult emergence (n = 71), 73.2% of them engaged in precopulatory mate guarding. In contrast, when males had previously experienced low density
after adult emergence (n = 82), 61.0% of them did not guard females. Mate guarding with physical contact occurred more frequently when males had previously
experienced a high density of potential rivals than when they had not, but the difference in behavior between the two groups
of males was marginally not significant. Nevertheless, these results suggest overall that T. kanzawai males change mate guarding behavior in response to previously experienced density. 相似文献
7.
RAC2-P38 MAPK-dependent NADPH oxidase activity is associated with the resistance of quiescent cells to ionizing radiation 总被引:1,自引:0,他引:1
Hailong Pei Jian Zhang Jing Nie Nan Ding Wentao Hu Junrui Hua 《Cell cycle (Georgetown, Tex.)》2017,16(1):113-122
Our recent study showed that quiescent G0 cells are more resistant to ionizing radiation than G1 cells; however, the underlying mechanism for this increased radioresistance is unknown. Based on the relatively lower DNA damage induced in G0 cells, we hypothesize that these cells are exposed to less oxidative stress during exposure. As a catalytic subunit of NADPH oxidase, Ras-related C3 botulinum toxin substrate 2 (RAC2) may be involved in the cellular response to ionizing radiation. Here, we show that RAC2 was expressed at low levels in G0 cells but increased substantially in G1 cells. Relative to G1 cells, the total antioxidant capacity in G0 phase cells increased upon exposure to X-ray radiation, whereas the intracellular concentration of ROS and malondialdehyde increased only slightly. The induction of DNA single- and double-stranded breaks in G1 cells by X-ray radiation was inhibited by knockdown of RAC2. P38 MAPK interaction with RAC2 resulted in a decrease of functional RAC2. Increased phosphorylation of P38 MAPK in G0 cells also increased cellular radioresistance; however, excessive production of ROS caused P38 MAPK dephosphorylation. P38 MAPK, phosphorylated P38 MAPK, and RAC2 regulated in mutual feedback and negative feedback regulatory pathways, resulting in the radioresistance of G0 cells. 相似文献
8.
Onur Basak Maaike van de Born Jeroen Korving Joep Beumer Stefan van der Elst Johan H van Es Hans Clevers 《The EMBO journal》2014,33(18):2057-2068
Cycling Lgr5+ stem cells fuel the rapid turnover of the adult intestinal epithelium. The existence of quiescent Lgr5+ cells has been reported, while an alternative quiescent stem cell population is believed to reside at crypt position +4. Here, we generated a novel Ki67RFP knock-in allele that identifies dividing cells. Using Lgr5-GFP;Ki67RFP mice, we isolated crypt stem and progenitor cells with distinct Wnt signaling levels and cell cycle features and generated their molecular signature using microarrays. Stem cell potential of these populations was further characterized using the intestinal organoid culture. We found that Lgr5high stem cells are continuously in cell cycle, while a fraction of Lgr5low progenitors that reside predominantly at +4 position exit the cell cycle. Unlike fast dividing CBCs, Lgr5low Ki67− cells have lost their ability to initiate organoid cultures, are enriched in secretory differentiation factors, and resemble the Dll1 secretory precursors and the label-retaining cells of Winton and colleagues. Our findings support the cycling stem cell hypothesis and highlight the cell cycle heterogeneity of early progenitors during lineage commitment. 相似文献
9.
10.
The definition of a quiescent centre (QC) in Arabidopsis has been adequately demonstrated. However, the QC structure of rice has not yet been described in detail. In this research, using histological and marker gene expression analysis, we concluded that the rice QC is very small, and is similar to that of Arabidopsis. Next we investigated the stability of the rice QC during nutrient deficiencies or external hormone treatments, and found that nutrient deficiencies, auxin treatment and cytokinin treatment did not change the cell patterns of the QC. However, ethylene induced irregular transverse cell divisions in the QC and changed formative cell divisions of the ground tissue stem cells (GTSCs) in rice. 相似文献