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1.
Plants (Basel) ; 12(24)2023 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-38140403

RESUMO

The continuous growth of roots depends on their ability to maintain a balanced ratio between cell production and cell differentiation at the tip. This process is regulated by the hormonal balance of cytokinin and auxin. However, other important regulators, such as plant folates, also play a regulatory role. In this study, we investigated the impact of the folate precursor para-aminobenzoic acid (PABA) on root development. Using pharmacological, genetic, and imaging approaches, we show that the growth of Arabidopsis thaliana roots is repressed by either supplementing the growth medium with PABA or overexpressing the PABA synthesis gene GAT-ADCS. This is associated with a smaller root meristem consisting of fewer cells. Conversely, reducing the levels of free root endogenous PABA results in longer roots with extended meristems. We provide evidence that PABA represses Arabidopsis root growth in a folate-independent manner and likely acts through two mechanisms: (i) the G2/M transition of cell division in the root apical meristem and (ii) promoting premature cell differentiation in the transition zone. These data collectively suggest that PABA plays a role in Arabidopsis root growth at the intersection between cell division and cell differentiation.

2.
Plant Physiol ; 178(3): 1370-1389, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30275058

RESUMO

Plants respond to gravitational force through directional growth along the gravity vector. Although auxin is the central component of the root graviresponse, it works in concert with other plant hormones. Here, we show that the folate precursor para-aminobenzoic acid (PABA) is a key modulator of the auxin-ethylene interplay during root gravitropism in Arabidopsis (Arabidopsis thaliana). In gravistimulated roots, PABA promotes an asymmetric auxin response, which causes the asymmetric growth responsible for root curvature. This activity requires the auxin response transcription factors AUXIN RESPONSE FACTOR7 (ARF7) and ARF19 as well as ethylene biosynthesis and signaling, indicating that PABA activity requires both auxin and ethylene pathways. Similar to ethylene, exogenous PABA reverses the agravitropic root growth of the auxin transport mutant pin-formed2 (pin2) and the auxin biosynthetic double mutant with loss of function of weak ethylene insensitive (wei) genes, wei8wei2, but not the pin2wei8wei2 triple mutant. This finding suggests that PABA regulates the ethylene-dependent reciprocal compensation between auxin transport and biosynthesis. Furthermore, manipulation of endogenous free PABA levels by modulating the expression of the gene encoding its glucosylation enzyme, UDP-GLYCOSYL TRANSFERASE75B1, impacts the root graviresponse, suggesting that endogenous free PABA levels may play a crucial role in modulating the auxin-ethylene cross talk necessary for root gravitropism.


Assuntos
Ácido 4-Aminobenzoico/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiologia , Etilenos/metabolismo , Gravitropismo , Ácidos Indolacéticos/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/genética , Transporte Biológico , Glucosiltransferases/genética , Glucosiltransferases/metabolismo , Gravitação , Fenótipo , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/fisiologia , Plântula/genética , Plântula/crescimento & desenvolvimento , Plântula/fisiologia , Transdução de Sinais , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
3.
New Phytol ; 217(4): 1610-1624, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29218850

RESUMO

Auxin gradients are sustained by series of influx and efflux carriers whose subcellular localization is sensitive to both exogenous and endogenous factors. Recently the localization of the Arabidopsis thaliana auxin efflux carrier PIN-FORMED (PIN) 6 was reported to be tissue-specific and regulated through unknown mechanisms. Here, we used genetic, molecular and pharmacological approaches to characterize the molecular mechanism(s) controlling the subcellular localization of PIN6. PIN6 localizes to endomembrane domains in tissues with low PIN6 expression levels such as roots, but localizes at the plasma membrane (PM) in tissues with increased PIN6 expression such as the inflorescence stem and nectary glands. We provide evidence that this dual localization is controlled by PIN6 phosphorylation and demonstrate that PIN6 is phosphorylated by mitogen-activated protein kinases (MAPKs) MPK4 and MPK6. The analysis of transgenic plants expressing PIN6 at PM or in endomembrane domains reveals that PIN6 subcellular localization is critical for Arabidopsis inflorescence stem elongation post-flowering (bolting). In line with a role for PIN6 in plant bolting, inflorescence stems elongate faster in pin6 mutant plants than in wild-type plants. We propose that PIN6 subcellular localization is under the control of developmental signals acting on tissue-specific determinants controlling PIN6-expression levels and PIN6 phosphorylation.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiologia , Membrana Celular/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Membrana Celular/efeitos dos fármacos , Retículo Endoplasmático/efeitos dos fármacos , Retículo Endoplasmático/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Interações Hidrofóbicas e Hidrofílicas , Hipocótilo/efeitos dos fármacos , Hipocótilo/metabolismo , Ácidos Indolacéticos/farmacologia , Inflorescência/efeitos dos fármacos , Inflorescência/metabolismo , Mutação com Perda de Função , Meristema/efeitos dos fármacos , Meristema/metabolismo , Fosforilação/efeitos dos fármacos , Fosfotreonina/metabolismo , Plantas Geneticamente Modificadas , Transporte Proteico/efeitos dos fármacos , Frações Subcelulares/metabolismo
4.
Plant Cell ; 25(11): 4451-68, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24249834

RESUMO

Glutathione is involved in thiol redox signaling and acts as a major redox buffer against reactive oxygen species, helping to maintain a reducing environment in vivo. Glutathione reductase (GR) catalyzes the reduction of glutathione disulfide (GSSG) into reduced glutathione (GSH). The Arabidopsis thaliana genome encodes two GRs: GR1 and GR2. Whereas the cytosolic/peroxisomal GR1 is not crucial for plant development, we show here that the plastid-localized GR2 is essential for root growth and root apical meristem (RAM) maintenance. We identify a GR2 mutant, miao, that displays strong inhibition of root growth and severe defects in the RAM, with GR activity being reduced to ∼50%. miao accumulates high levels of GSSG and exhibits increased glutathione oxidation. The exogenous application of GSH or the thiol-reducing agent DTT can rescue the root phenotype of miao, demonstrating that the RAM defects in miao are triggered by glutathione oxidation. Our in silico analysis of public microarray data shows that auxin and glutathione redox signaling generally act independently at the transcriptional level. We propose that glutathione redox status is essential for RAM maintenance through both auxin/PLETHORA (PLT)-dependent and auxin/PLT-independent redox signaling pathways.


Assuntos
Arabidopsis/metabolismo , Glutationa Redutase/metabolismo , Glutationa/metabolismo , Meristema/metabolismo , Raízes de Plantas/metabolismo , Plastídeos/enzimologia , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Glutationa Redutase/genética , Ácidos Indolacéticos/farmacologia , Mutação , Oxirredução , Raízes de Plantas/crescimento & desenvolvimento , Plantas Geneticamente Modificadas
5.
Proc Natl Acad Sci U S A ; 105(48): 18818-23, 2008 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-19033199

RESUMO

Lateral roots are initiated postembryonically in response to environmental cues, enabling plants to explore efficiently their underground environment. However, the mechanisms by which the environment determines the position of lateral root formation are unknown. In this study, we demonstrate that in Arabidopsis thaliana lateral root initiation can be induced mechanically by either gravitropic curvature or by the transient bending of a root by hand. The plant hormone auxin accumulates at the site of lateral root induction before a primordium starts to form. Here we describe a subcellular relocalization of PIN1, an auxin transport protein, in a single protoxylem cell in response to gravitropic curvature. This relocalization precedes auxin-dependent gene transcription at the site of a new primordium. Auxin-dependent nuclear signaling is necessary for lateral root formation; arf7/19 double knock-out mutants normally form no lateral roots but do so upon bending when the root tip is removed. Signaling through arf7/19 can therefore be bypassed by root bending. These data support a model in which a root-tip-derived signal acts on downstream signaling molecules that specify lateral root identity.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Gravitropismo , Meristema/crescimento & desenvolvimento , Raízes de Plantas/crescimento & desenvolvimento , Transdução de Sinais/fisiologia , Arabidopsis/anatomia & histologia , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Ácidos Indolacéticos/metabolismo , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Meristema/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Raízes de Plantas/anatomia & histologia , Raízes de Plantas/metabolismo , Brotos de Planta/anatomia & histologia , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Estresse Mecânico
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