Cytokinins regulate root growth through its action on meristematic cell proliferation but not on the transition to differentiation

2018 ◽  
Vol 45 (2) ◽  
pp. 215 ◽  
Author(s):  
Victor B. Ivanov ◽  
Alexey N. Filin
Keyword(s):  
Cell Proliferation ◽  
Root Growth ◽  
Life Span ◽  
Mitotic Cycle ◽  
Meristematic Cell ◽  
Cycle Duration ◽  
Triple Mutant ◽  
Cytokinin Synthesis ◽  
Transition To Elongation ◽  
Cell Transition

Contrary to the wide-spread view that cytokinins change the rate of root growth and meristem size by regulating the cell transition to elongation (differentiation), our data showed that cytokinins affected the cell cycle duration in the meristem. The rate of meristematic cell transition to elongation itself is regulated by two groups of independent processes, through influence on (i) the life-span of cells in the meristem, and (ii) the cell proliferation rate in the meristem. Trans-zeatin slows down the root growth rate and the cell transition to elongation as a result of prolongation of mitotic cycles. The life-span of cells in the meristem does not change. The number of meristematic cells in one file decreases due to inhibition of cell proliferation but not to an acceleration of cell transition to elongation. Roots of triple mutant ipt3ipt5ipt7, in which cytokinin synthesis is slowed down, behave in an opposite way such that the rate of cell transition to elongation and cell proliferation is speeded up. Their peculiarity is that the life-span of cells in meristem becomes shorter than in control roots. In both cases, a change in concentration of endogenous cytokinin or in its signalling are associated with a change in mitotic cycle duration.

scholarly journals RADIATION EFFECTS ON THE GROWTH RATE AND CELL POPULATION KINETICS OF ACTIVELY GROWING AND DORMANT ROOTS OF TRADESCANTIA PALUDOSA

1965 ◽  
Vol 26 (1) ◽  
pp. 187-199 ◽  
Author(s):  
Jack Van't Hof ◽  
A. H. Sparrow
Keyword(s):  
Growth Rate ◽  
Root Growth ◽  
Cell Population ◽  
Mitotic Cycle ◽  
Tritiated Thymidine ◽  
Cycle Duration ◽  
X Rays ◽  
Proliferating Cells ◽  
Population Kinetics ◽  
Tradescantia Paludosa

Actively growing and dormant roots of Tradescantia paludosa were exposed to x-rays to compare the radiosensitivity of an actively proliferating tissue with that of one which is not active but is potentially proliferative. The level of effect was ascertained by the degree of change in the rate of root growth 4 days after exposure. Cell population kinetics were measured in control and in irradiated roots to determine whether or not a change was produced either in the number of proliferating cells or in the mitotic cycle duration which was sufficient to explain the altered rate of root growth. Nuclear volumes were also measured to provide an estimate of the relative total target size in actively growing vs. dormant roots. Tritiated thymidine was used to measure the cycle duration and the proportion of cells synthesizing DNA. The results showed that 184 and 305 r respectively were required to reduce the linear root growth rate to 37 per cent of that of the control for actively growing and dormant roots. Mitotic cycle duration, measured 4 days after x-ray exposure, was the same as in the control. The number of proliferating cells, however, was reduced. The rate of cell production in the irradiated roots was reduced to approximately one-half that of the controls. The average nuclear volumes of active and dormant roots were 733 and 491 µ3 respectively; thus the difference in the number of roentgens required to reduce growth to 37 per cent of that of the control can be attributed to the different average nuclear volumes. Therefore, the experiments suggest that part if not most of the differences in sensitivity between an actively dividing and an essentially non-dividing meristematic cell population resides in their different average nuclear volumes. Thus the law of Bergonie and Tribondeau needs to be reinterpreted, since the basic reason for the differences is secondary to whether or not the meristematic cells are proliferating.

scholarly journals Lateral Root Priming Synergystically Arises from Root Growth and Auxin Transport Dynamics

2018 ◽  
Author(s):  
Thea van den Berg ◽  
Kirsten H. ten Tusscher
Keyword(s):  
Cell Cycle ◽  
Root Growth ◽  
Lateral Root ◽  
Root Formation ◽  
Growth Dynamics ◽  
Root Tip ◽  
Cycle Duration ◽  
Elongation Zone ◽  
Lateral Root Formation ◽  
Cell Cycle Duration

AbstractThe root system is a major determinant of plant fitness. Its capacity to supply the plant with sufficient water and nutrients strongly depends on root system architecture, which arises from the repeated branching off of lateral roots. A critical first step in lateral root formation is priming, which prepatterns sites competent of forming a lateral root. Priming is characterized by temporal oscillations in auxin, auxin signalling and gene expression in the root meristem, which through growth become transformed into a spatially repetitive pattern of competent sites. Previous studies have demonstrated the importance of auxin synthesis, transport and perception for the amplitude of these oscillations and their chances of producing an actual competent site. Additionally, repeated lateral root cap apoptosis was demonstrated to be strongly correlated with repetitive lateral root priming. Intriguingly, no single mutation has been identified that fully abolishes lateral root formation, and thusfar the mechanism underlying oscillations has remained unknown. In this study, we investigated the impact of auxin reflux loop properties combined with root growth dynamics on priming, using a computational approach. To this end we developed a novel multi-scale root model incorporating a realistic root tip architecture and reflux loop properties as well as root growth dynamics. Excitingly, in this model, repetitive auxin elevations automatically emerge. First, we show that root tip architecture and reflux loop properties result in an auxin loading zone at the start of the elongation zone, with preferential auxin loading in narrow vasculature cells. Second, we demonstrate how meristematic root growth dynamics causes regular alternations in the sizes of cells arriving at the elongation zone, which subsequently become amplified during cell expansion. These cell size differences translate into differences in cellular auxin loading potential. Combined, these properties result in temporal and spatial fluctuations in auxin levels in vasculature and pericycle cells. Our model predicts that temporal priming frequency predominantly depends on cell cycle duration, while cell cycle duration together with meristem size control lateral root spacing.

Reversible inhibition of root growth and cell proliferation by pentavalent arsenic in Allium cepa L.

1988 ◽  
Vol 28 (1) ◽  
pp. 9-18 ◽  
Author(s):  
I. Pepper ◽  
N. Galanti ◽  
J. Sans ◽  
J.F. Lopez-Saez
Keyword(s):  
Cell Proliferation ◽  
Root Growth ◽  
Allium Cepa ◽  
Reversible Inhibition ◽  
Allium Cepa L ◽  
Pentavalent Arsenic

scholarly journals Nitrogen Deficiency-Induced Decrease in Cytokinins Content Promotes Rice Seminal Root Growth by Promoting Root Meristem Cell Proliferation and Cell Elongation

Cells ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 916
Author(s):  
Qi Wang ◽  
Yanchun Zhu ◽  
Xiao Zou ◽  
Fengfeng Li ◽  
Jialiang Zhang ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Root Growth ◽  
Cell Elongation ◽  
Developmental Plasticity ◽  
Root Meristem ◽  
Seminal Root ◽  
Down Regulation ◽  
Meristem Cell ◽  
Root Meristem Cell ◽  
N Deficiency

Rice (Oryza sativa L.) seedlings grown under nitrogen (N) deficiency conditions show a foraging response characterized by increased root length. However, the mechanism underlying this developmental plasticity is still poorly understood. In this study, the mechanism by which N deficiency influences rice seminal root growth was investigated. The results demonstrated that compared with the control (1 mM N) treatment, N deficiency treatments strongly promoted seminal root growth. However, the N deficiency-induced growth was negated by the application of zeatin, which is a type of cytokinin (CK). Moreover, the promotion of rice seminal root growth was correlated with a decrease in CK content, which was due to the N deficiency-mediated inhibition of CK biosynthesis through the down-regulation of CK biosynthesis genes and an enhancement of CK degradation through the up-regulation of CK degradation genes. In addition, the N deficiency-induced decrease in CK content not only enhanced the root meristem cell proliferation rate by increasing the meristem cell number via the down-regulation of OsIAA3 and up-regulation of root-expressed OsPLTs, but also promoted root cell elongation by up-regulating cell elongation-related genes, including root-specific OsXTHs and OsEXPs. Taken together, our data suggest that an N deficiency-induced decrease in CK content promotes the seminal root growth of rice seedlings by promoting root meristem cell proliferation and cell elongation.

scholarly journals The Mitotic Cycle Duration inVicia FabaRoot-Tip Meristems with Different Sized Chromosomes

Caryologia ◽  
1972 ◽  
Vol 25 (4) ◽  
pp. 445-453 ◽  
Author(s):  
M. D. Bennett ◽  
J. B. Smith ◽  
D. Smith
Keyword(s):  
Mitotic Cycle ◽  
Cycle Duration

Influence of long-term limitation of cell proliferation on the cell cycle duration

1995 ◽  
Vol 28 (8) ◽  
pp. 431-435 ◽  
Author(s):  
A. V. Blokhin ◽  
A. V. Khalyavkin
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cycle Duration ◽  
Cell Cycle Duration ◽  
Term Limitation

scholarly journals Salt Stress Promotes Abscisic Acid Accumulation to Affect Cell Proliferation and Expansion of Primary Roots in Rice

2021 ◽  
Vol 22 (19) ◽  
pp. 10892
Author(s):  
Yingying Huang ◽  
Jiahao Zhou ◽  
Yuxiang Li ◽  
Ruidang Quan ◽  
Juan Wang ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Abscisic Acid ◽  
Salt Stress ◽  
Root Growth ◽  
Essential Role ◽  
Primary Root ◽  
Microscopic Analysis ◽  
Root Apical Meristem ◽  
Aba Signaling ◽  
Rice Varieties

The primary root is the basic component of the root system and plays a key role in early seedling growth in rice. Its growth is easily affected by environmental cues, such as salt stress. Abscisic acid (ABA) plays an essential role in root development, but the molecular mechanism underlying ABA-regulated root growth in response to salt stress remains poorly understood. In this study, we report that salt stress inhibits primary root elongation and promotes primary root swelling. Moreover, salt stress induces the expression of ABA-responsive genes and ABA accumulation in the primary root, revealing that ABA plays an essential role in salt-modulated root growth. Transgenic lines of OsSAPK10-OE and OsABIL2-OE, which constitutively express OsSAPK10 or OsABIL2, with enhanced or attenuated ABA signaling, show increased and decreased sensitivity to salt, correspondingly. Microscopic analysis indicates that salt and ABA inhibits cell proliferation and promotes cell expansion in the root apical meristem. Transcriptome analysis showed that ABA induces the expression of EXPANSIN genes. Further investigations indicate that ABA exerts these effects largely through ABA signaling. Thus, our findings deepen our understanding of the role of ABA in controlling primary root growth in response to salt stress, and this knowledge can be used by breeders to cultivate rice varieties suitable for saline–alkali land.

Influence of long-term limitation of cell proliferation on the cell cycle duration

1996 ◽  
Vol 29 (1) ◽  
pp. 59-59
Author(s):  
A. V. Blokhin ◽  
A. V. Khalyavkin
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cycle Duration ◽  
Cell Cycle Duration ◽  
Term Limitation

scholarly journals Lipopolysaccharide-induced inflammation attenuates taste progenitor cell proliferation and shortens the life span of taste bud cells

2010 ◽  
Vol 11 (1) ◽  
pp. 72 ◽  
Author(s):  
Zachary J Cohn ◽  
Agnes Kim ◽  
Liquan Huang ◽  
Joseph Brand ◽  
Hong Wang
Keyword(s):  
Cell Proliferation ◽  
Life Span ◽  
Progenitor Cell ◽  
Taste Bud ◽  
Progenitor Cell Proliferation ◽  
Taste Bud Cells
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