scholarly journals Supraoptimal Brassinosteroid Levels Inhibit Root Growth by Reducing Root Meristem and Cell Elongation in Rice

Plants ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1962
Author(s):  
Kewalee Jantapo ◽  
Watcharapong Wimonchaijit ◽  
Wenfei Wang ◽  
Juthamas Chaiwanon
Keyword(s):  
Cell Proliferation ◽  
Root Growth ◽  
Cell Elongation ◽  
Root Meristem ◽  
Oryza Sativa L ◽  
Rice Root ◽  
Meristem Size ◽  
A Genome ◽  
Meristem Development ◽  
N Deficiency

Root growth depends on cell proliferation and cell elongation at the root meristem, which are controlled by plant hormones and nutrient availability. As a foraging strategy, rice (Oryza sativa L.) grows longer roots when nitrogen (N) is scarce. However, how the plant steroid hormone brassinosteroid (BR) regulates rice root meristem development and responses to N deficiency remains unclear. Here, we show that BR has a negative effect on meristem size and a dose-dependent effect on cell elongation in roots of rice seedlings treated with exogenous BR (24-epicastasterone, ECS) and the BR biosynthesis inhibitor propiconazole (PPZ). A genome-wide transcriptome analysis identified 4110 and 3076 differentially expressed genes in response to ECS and PPZ treatments, respectively. The gene ontology (GO) analysis shows that terms related to cell proliferation and cell elongation were enriched among the ECS-repressed genes. Furthermore, microscopic analysis of ECS- and PPZ-treated roots grown under N-sufficient and N-deficient conditions demonstrates that exogenous BR or PPZ application could not enhance N deficiency-mediated root elongation promotion as the treatments could not promote root meristem size and cell elongation simultaneously. Our study demonstrates that optimal levels of BR in the rice root meristem are crucial for optimal root growth and the foraging response to N deficiency.

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 Supraoptimal Cytokinin Content Inhibits Rice Seminal Root Growth by Reducing Root Meristem Size and Cell Length via Increased Ethylene Content

2018 ◽  
Vol 19 (12) ◽  
pp. 4051 ◽  
Author(s):  
Xiao Zou ◽  
Junwei Shao ◽  
Qi Wang ◽  
Peisai Chen ◽  
Yanchun Zhu ◽  
...  
Keyword(s):  
Root Growth ◽  
Cell Elongation ◽  
Root Meristem ◽  
Ethylene Biosynthesis ◽  
Cell Length ◽  
Seminal Root ◽  
Dependent Manner ◽  
Meristem Size ◽  
Dose Dependent ◽  
Ethylene Level

Cytokinins (CKs), a class of phytohormone, regulate root growth in a dose-dependent manner. A certain threshold content of CK is required for rapid root growth, but supraoptimal CK content inhibits root growth, and the mechanism of this inhibition remains unclear in rice. In this study, treatments of lovastatin (an inhibitor of CK biosynthesis) and kinetin (KT; a synthetic CK) were found to inhibit rice seminal root growth in a dose-dependent manner, suggesting that endogenous CK content is optimal for rapid growth of the seminal root in rice. KT treatment strongly increased ethylene level by upregulating the transcription of ethylene biosynthesis genes. Ethylene produced in response to exogenous KT inhibited rice seminal root growth by reducing meristem size via upregulation of OsIAA3 transcription and reduced cell length by downregulating transcription of cell elongation-related genes. Moreover, the effects of KT treatment on rice seminal root growth, root meristem size and cell length were rescued by treatment with aminoethoxyvinylglycine (an inhibitor of ethylene biosynthesis), which restored ethylene level and transcription levels of OsIAA3 and cell elongation-related genes. Supraoptimal CK content increases ethylene level by promoting ethylene biosynthesis, which in turn inhibits rice seminal root growth by reducing root meristem size and cell length.

scholarly journals ABA represses TOR and root meristem activity through nuclear exit of the SnRK1 kinase

2021 ◽  
Author(s):  
Borja Belda-Palazon ◽  
Monica Costa ◽  
Tom Beeckman ◽  
Filip Rolland ◽  
Elena Baena-Gonzalez
Keyword(s):  
Cell Proliferation ◽  
Nuclear Export ◽  
Growth Regulation ◽  
Root Meristem ◽  
Plant Tolerance ◽  
Proliferation Zone ◽  
Meristem Size ◽  
Main Driver ◽  
Root Meristematic Cells ◽  
Underlying Mechanisms

The phytohormone abscisic acid (ABA) promotes plant tolerance to major stresses like drought, partly by modulating plant growth and development. However, the underlying mechanisms are poorly understood. Here, we show that cell proliferation in the Arabidopsis thaliana root meristem is controlled by the interplay between three kinases, SNF1-RELATED KINASE 2 (SnRK2), the main driver of ABA signaling, the SnRK1 energy sensor, and the growth-promoting TARGET OF RAPAMYCIN (TOR) kinase. Under favorable conditions, the SnRK1α1 catalytic subunit is enriched in the nuclei of root meristematic cells and this is accompanied by normal cell proliferation and meristem size. Depletion of SnRK2s in a snrk2.2 snrk2.3 double mutant causes constitutive cytoplasmic localization of SnRK1α1 and a reduction in meristem size, suggesting that, under non-stress conditions, SnRK2s enable growth by retaining SnRK1α1 in the nucleus. In response to elevated ABA levels, SnRK1α1 translocates to the cytoplasm and this is accompanied by inhibition of TOR, decreased cell proliferation and meristem size. Blocking nuclear export with leptomycin B abrogates ABA-driven SnRK1α1 relocalization to the cytoplasm and the inhibition of TOR. Fusion of SnRK1α1 to an SV40 nuclear localization signal leads to defective TOR repression in response to ABA, demonstrating that SnRK1α1 nuclear exit is a premise for this repression. Finally, the SnRK2-dependent changes in SnRK1α1 subcellular localization are specific to the proliferation zone of the meristem, underscoring the relevance of this mechanism for growth regulation.

scholarly journals Root meristem growth factor 1 controls root meristem size through reactive oxygen species signaling

2018 ◽  
Author(s):  
Masashi Yamada ◽  
Xinwei Han ◽  
Philip. N. Benfey
Keyword(s):  
Reactive Oxygen Species ◽  
Transcription Factor ◽  
Stem Cell ◽  
Growth Factor ◽  
Root Meristem ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Meristem Size ◽  
Essential Question ◽  
Meristem Development

AbstractStem cell niche and root meristem size are maintained by intercellular interactions and signaling networks of a plant peptide hormone, Root Meristem Growth Factor 1 (RGF1). How RGF1 regulates root meristem development is an essential question to understand stem cell function. Although five receptors of RGF1 have recently been identified, the downstream signaling mechanism remains unknown. Here, we report a series of signaling events following RGF1 action. The RGF1-receptor pathway controls distribution of reactive oxygen species (ROS) along the developmental zones of the Arabidopsis root. We identify a novel transcription factor, RGF1 INDUCIBLE TRANSCRIPTION FACTOR 1 (RITF1), which plays a central role in mediating RGF1 signaling. Manipulating RITF1 expression leads to redistribution of ROS along the root developmental zones. Changes in ROS distribution, in turn, enhance the stability of the PLETHORA2 (PLT2) protein, a master regulator of root stem cells. Taken together, our study clearly depicts a signaling cascade initiated by RGF1 and links the RGF1 peptide to ROS regulatory mechanisms.

scholarly journals SHOEBOX Modulates Root Meristem Size in Rice through Dose-Dependent Effects of Gibberellins on Cell Elongation and Proliferation

PLoS Genetics ◽  
2015 ◽  
Vol 11 (8) ◽  
pp. e1005464 ◽  
Author(s):  
Jintao Li ◽  
Yu Zhao ◽  
Huangwei Chu ◽  
Likai Wang ◽  
Yanru Fu ◽  
...  
Keyword(s):  
Cell Elongation ◽  
Root Meristem ◽  
Meristem Size ◽  
Dose Dependent

scholarly journals Actin isovariant ACT7 regulates root meristem development in Arabidopsis through modulating auxin and ethylene responses

2021 ◽  
Author(s):  
Takahiro Numata ◽  
Kenji Sugita ◽  
Arifa Ahamed Rahman ◽  
Abidur Rahman
Keyword(s):  
Cell Division ◽  
Cell Elongation ◽  
Root Meristem ◽  
Primary Role ◽  
Arabidopsis Root ◽  
Meristem Development ◽  
Constant Cell ◽  
Division Cell ◽  
Auxin Efflux Carriers

Meristem, which sustains a reservoir of niche cells at its apex, is the most functionally dynamic part in a plant body. The shaping of the meristem requires constant cell division and cell elongation, that are regulated by hormones and cell cytoskeletal components, actin. Although the roles of hormones in regulating meristem development have been extensively studied, the role of actin in this process is still elusive. Using the single and double mutants of the vegetative class actin, we demonstrate that ACT7 plays a primary role in regulating the root meristem development. In absence of ACT7, but not ACT8 and ACT2, cellular depolymerization of actin is observed. Consistently, act7 mutant shows reduced cell division, cell elongation and meristem length. Intracellular distribution and trafficking of auxin transport proteins in the actin mutants revealed that ACT7 specifically functions in root meristem to facilitate the trafficking of auxin efflux carriers PIN1 and PIN2, and consequently the transport of auxin. Compared with act7, act7act8 double mutant shows slightly enhanced phenotypic response and altered intracellular trafficking. The altered distribution of auxin in act7 and act7act8 affects the roots response to ethylene but not to cytokinin. Collectively, our results suggest that Arabidopsis root meristem development is primarily controlled through actin isovariant ACT7 mediated modulation of auxin-ethylene response.

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