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1.
Plant Cell Physiol ; 61(2): 342-352, 2020 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-31730198

RESUMEN

Nitrate can act as a potent signal to control growth and development in plants. In this study, we show that nitrate is able to stimulate primary root growth via increased meristem activity and cytokinin signaling. Cytokinin perception and biosynthesis mutants displayed shorter roots as compared with wild-type plants when grown with nitrate as the only nitrogen source. Histological analysis of the root tip revealed decreased cell division and elongation in the cytokinin receptor double mutant ahk2/ahk4 as compared with wild-type plants under a sufficient nitrate regime. Interestingly, a nitrate-dependent root growth arrest was observed between days 5 and 6 after sowing. Wild-type plants were able to recover from this growth arrest, while cytokinin signaling or biosynthesis mutants were not. Transcriptome analysis revealed significant changes in gene expression after, but not before, this transition in contrasting genotypes and nitrate regimes. We identified genes involved in both cell division and elongation as potentially important for primary root growth in response to nitrate. Our results provide evidence linking nitrate and cytokinin signaling for the control of primary root growth in Arabidopsis thaliana.


Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Citocininas/biosíntesis , Nitratos/metabolismo , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Transducción de Señal/fisiología , Arabidopsis/genética , Proteínas de Arabidopsis/genética , División Celular , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Histidina Quinasa/metabolismo , Meristema/metabolismo , Mutación , Raíces de Plantas/citología , Proteínas Quinasas/metabolismo , Receptores de Superficie Celular/metabolismo
2.
J Exp Bot ; 63(8): 3109-25, 2012 May.
Artículo en Inglés | MEDLINE | ID: mdl-22371077

RESUMEN

Aluminium (Al) toxicity and drought are two major factors limiting common bean (Phaseolus vulgaris) production in the tropics. Short-term effects of Al toxicity and drought stress on root growth in acid, Al-toxic soil were studied, with special emphasis on Al-drought interaction in the root apex. Root elongation was inhibited by both Al and drought. Combined stresses resulted in a more severe inhibition of root elongation than either stress alone. This result was different from the alleviation of Al toxicity by osmotic stress (-0.60 MPa polyethylene glycol) in hydroponics. However, drought reduced the impact of Al on the root tip, as indicated by the reduction of Al-induced callose formation and MATE expression. Combined Al and drought stress enhanced up-regulation of ACCO expression and synthesis of zeatin riboside, reduced drought-enhanced abscisic acid (ABA) concentration, and expression of NCED involved in ABA biosynthesis and the transcription factors bZIP and MYB, thus affecting the regulation of ABA-dependent genes (SUS, PvLEA18, KS-DHN, and LTP) in root tips. The results provide circumstantial evidence that in soil, drought alleviates Al injury, but Al renders the root apex more drought-sensitive, particularly by impacting the gene regulatory network involved in ABA signal transduction and cross-talk with other phytohormones necessary for maintaining root growth under drought.


Asunto(s)
Aluminio/toxicidad , Citocininas/biosíntesis , Sequías , Phaseolus/genética , Phaseolus/fisiología , Estrés Fisiológico/efectos de los fármacos , Estrés Fisiológico/genética , Ácido Abscísico/biosíntesis , Vías Biosintéticas/efectos de los fármacos , Vías Biosintéticas/genética , Pared Celular/efectos de los fármacos , Pared Celular/genética , Colombia , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Genes de Plantas/genética , Genotipo , Glucanos/metabolismo , Isopenteniladenosina/análogos & derivados , Isopenteniladenosina/metabolismo , Modelos Biológicos , Presión Osmótica/efectos de los fármacos , Phaseolus/efectos de los fármacos , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/fisiología , Plantones/efectos de los fármacos , Plantones/crecimiento & desarrollo
3.
Plant Cell Rep ; 29(11): 1227-34, 2010 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-20690021

RESUMEN

Auxin induces in vitro somatic embryogenesis in coconut plumular explants through callus formation. Embryogenic calli and non-embryogenic calli can be formed from the initial calli. Analysis of endogenous cytokinins showed the occurrence of cytokinins with aromatic and aliphatic side chains. Fourteen aliphatic cytokinins and four aromatic cytokinins were analysed in the three types of calli and all the cytokinins were found in each type, although some in larger proportions than others. The most abundant cytokinins in each type of callus were isopentenyladenine-9-glucoside, zeatin-9-glucoside, zeatin riboside, isopentenyladenine riboside, dihydrozeatin and dihydrozeatin riboside in decreasing order. Total cytokinin content was compared between the three types of calli, and it was found to be lower in embryogenic calli compared to non-embryogenic calli or initial calli. The same pattern was observed for individual cytokinins. When explants were cultured in media containing exogenously added cytokinins, the formation of embryogenic calli in the explants was reduced. When 8-azaadenine (an anticytokinin) was added the formation of embryogenic calli and somatic embryos was increased. These results suggest that the difference in somatic embryo formation capacity observed between embryogenic calli and non-embryogenic calli is related to their endogenous cytokinin contents.


Asunto(s)
Cocos/química , Citocininas/análisis , Técnicas de Embriogénesis Somática de Plantas/métodos , Adenina/análogos & derivados , Adenina/farmacología , Cocos/crecimiento & desarrollo , Medios de Cultivo , Citocininas/biosíntesis
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