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      Multiplicacion in vitro de agave cocui trelease a traves de yemas axilares Translated title: In vitro multiplication of agave cocui trelease through axillary buds

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          Abstract

          El cocuy, Agave cocui Trelease es importante para las zonas semiaridas del centro-occidente de Venezuela. Involucra sistemas de produccion tradicional de licor, jabon, conservas, entre otros. Soportando economicamente muchas familias en el estado Lara. La produccion se basa en plantas creciendo naturalmente, con suplencia de materia prima limitada. Para aumentar la disponibilidad de plantas e incrementar la actividad economica de estas comunidades rurales, sistemas de propagacion asexual han sido implementados, con una tasa de crecimiento lenta y la produccion de plantas no cubre la demanda. Un sistema de propagacion in vitro usando yemas axilares se ha establecido. Las yemas se colocaron en medio Murashige y Skoog (MS) suplementado con tiamina (1 mg l-1), acido nicotinico (1mg l-1), piridoxina-HCl (1 mg l-1), mio-inositol (100 mg l-1), BA (1 mg l-1), ANA (1 mg l-1) sacarosa (30 g l-1) y Agar (5g l-1). Cuarenta explantes fueron cultivados en 10 ml del medio de cultivo, y sembrados en la oscuridad por 7 dias. Las yemas se transfirieron a luz fluorescente (16,95 W.m-2), 28 ± 2 ºC y fotoperiodo de 16 h. Los brotes fueron evidentes 1 mes posterior al cultivo in vitro, y 6 brotes en promedio se observaron por yema cultivada. La tasa de brotacion aumento cuando la temperatura subio a 40 ºC. Plantas completas se obtuvieron en medio sin hormonas. El transplante a suelo (1:1:1 de suelo:arena: aserrin de coco) permitio la aclimatacion de las plantas en 1 semana. Todas las plantas tuvieron morfologia normal, por lo que el cultivo in vitro de yemas axilares se puede decir es un metodo eficiente para propagar A. cocui Trelease

          Translated abstract

          The cocuy, Agave cocui Trelease is an important crop for the semiarid zones of the central-west part of Venezuela. It is involved in a traditional production systems for liquor, soap, preserves, among others. It is the economical support of many families in Lara State, Venezuela. Normally, the production was based in naturally occurring plants, so supply of plants is limited. In order to increase plant supply and improve the economical activity of these rural communities, asexual propagation systems have been implemented with slow growth rate and plant production not enough to satisfy the demand. A mass propagation system using axillary buds have been established. Buds were placed on Murashige and Skoog (MS) medium supplemented with thyamine (1mg l-1), nicotinic acid (1mg l-1), pyridoxine HCl (1mg l-1), inositol (100mg l-1), BA (1mg l-1), ANA (1mg l-1) sucrose (30 g l-1) and Agar (5g l-1). Forty explants were cultured in 10ml of culture medium, and were placed in the dark for 7 days. Buds were placed under fluorescent light (16.95 W.m-2), at 28 ± 2 ºC and a 16 hr photoperiod. Shoots were observed 1 months after culture, an average of 6 shoots were observed for each cultured axillary bud. Sprouting ratio was increased when temperatures was increased to 40 ºC. Complete plants were obtained by transferring shoots to medium with no hormones. Transplant to soil (1:1:1 soil:sand:coconut sawdust) allowed plants to be acclimatized in 1 week. All plants have normal morphology. As a conclusion axillary bud in vitro culture can be referred as an efficient method to propagate A. cocui Trelease

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          Most cited references29

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          Role of cytokinin and auxin in shaping root architecture: regulating vascular differentiation, lateral root initiation, root apical dominance and root gravitropism.

          Development and architecture of plant roots are regulated by phytohormones. Cytokinin (CK), synthesized in the root cap, promotes cytokinesis, vascular cambium sensitivity, vascular differentiation and root apical dominance. Auxin (indole-3-acetic acid, IAA), produced in young shoot organs, promotes root development and induces vascular differentiation. Both IAA and CK regulate root gravitropism. The aims of this study were to analyse the hormonal mechanisms that induce the root's primary vascular system, explain how differentiating-protoxylem vessels promote lateral root initiation, propose the concept of CK-dependent root apical dominance, and visualize the CK and IAA regulation of root gravitropiosm. The hormonal analysis and proposed mechanisms yield new insights and extend previous concepts: how the radial pattern of the root protoxylem vs. protophloem strands is induced by alternating polar streams of high IAA vs. low IAA concentrations, respectively; how differentiating-protoxylem vessel elements stimulate lateral root initiation by auxin-ethylene-auxin signalling; and how root apical dominance is regulated by the root-cap-synthesized CK, which gives priority to the primary root in competition with its own lateral roots. CK and IAA are key hormones that regulate root development, its vascular differentiation and root gravitropism; these two hormones, together with ethylene, regulate lateral root initiation.
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            Cytokinins act directly on lateral root founder cells to inhibit root initiation.

            In Arabidopsis thaliana, lateral roots are formed from root pericycle cells adjacent to the xylem poles. Lateral root development is regulated antagonistically by the plant hormones auxin and cytokinin. While a great deal is known about how auxin promotes lateral root development, the mechanism of cytokinin repression is still unclear. Elevating cytokinin levels was observed to disrupt lateral root initiation and the regular pattern of divisions that characterizes lateral root development in Arabidopsis. To identify the stage of lateral root development that is sensitive to cytokinins, we targeted the expression of the Agrobacterium tumefaciens cytokinin biosynthesis enzyme isopentenyltransferase to either xylem-pole pericycle cells or young lateral root primordia using GAL4-GFP enhancer trap lines. Transactivation experiments revealed that xylem-pole pericycle cells are sensitive to cytokinins, whereas young lateral root primordia are not. This effect is physiologically significant because transactivation of the Arabidopsis cytokinin degrading enzyme cytokinin oxidase 1 in lateral root founder cells results in increased lateral root formation. We observed that cytokinins perturb the expression of PIN genes in lateral root founder cells and prevent the formation of an auxin gradient that is required to pattern lateral root primordia.
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              Histidine kinase homologs that act as cytokinin receptors possess overlapping functions in the regulation of shoot and root growth in Arabidopsis.

              Cytokinins are plant hormones that may play essential and crucial roles in various aspects of plant growth and development. Although the functional significance of exogenous cytokinins as to the proliferation and differentiation of cells has been well documented, the biological roles of endogenous cytokinins have remained largely unknown. The recent discovery of the Arabidopsis Histidine Kinase 4 (AHK4)/CRE1/WOL cytokinin receptor in Arabidopsis thaliana strongly suggested that the cellular response to cytokinins involves a two-component signal transduction system. However, the lack of an apparent phenotype in the mutant, presumably because of genetic redundancy, prevented us from determining the in planta roles of the cytokinin receptor. To gain insight into the molecular functions of the three AHK genes AHK2, AHK3, and AHK4 in this study, we identified mutational alleles of the AHK2 and AHK3 genes, both of which encode sensor histidine kinases closely related to AHK4, and constructed a set of multiple ahk mutants. Application of exogenous cytokinins to the resultant strains revealed that both AHK2 and AHK3 function as positive regulators for cytokinin signaling similar to AHK4. The ahk2 ahk4 and ahk3 ahk4 double mutants and the ahk single mutants grew normally, whereas the ahk2 ahk3 double mutants exhibited a semidwarf phenotype as to shoots, such as a reduced leaf size and a reduced influorescence stem length. The growth and development of the ahk2 ahk3 ahk4 triple mutant were markedly inhibited in various tissues and organs, including the roots and leaves in the vegetative growth phase and the influorescence meristem in the reproductive phase. We showed that the inhibition of growth is associated with reduced meristematic activity of cells. Expression analysis involving AHK:beta-glucuronidase fusion genes suggested that the AHK genes are expressed ubiquitously in various tissues during postembryonic growth and development. Our results thus strongly suggest that the primary functions of AHK genes, and those of endogenous cytokinins, are triggering of the cell division and maintenance of the meristematic competence of cells to prevent subsequent differentiation until a sufficient number of cells has accumulated during organogenesis. Copyright 2004 American Society of Plant Biologists
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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Journal
                at
                Agronomía Tropical
                Agronomía Trop.
                Instituto Nacional de Investigaciones Agrícolas INIA de Venezuela (Maracay )
                0002-192X
                June 2009
                : 59
                : 2
                : 129-135
                Affiliations
                [1 ] INIA-CENIAP Venezuela
                [2 ] INIA LARA Venezuela
                Article
                S0002-192X2009000200002
                9036f969-bfb6-4f7a-af24-195e104d9457

                http://creativecommons.org/licenses/by/4.0/

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                SciELO Venezuela

                Self URI (journal page): http://www.scielo.org.ve/scielo.php?script=sci_serial&pid=0002-192X&lng=en
                Categories
                AGRONOMY

                Horticulture
                Cocuy,in vitro culture,meristems,axilarry buds,micropropagation,cultivo in vitro,meristemas,yemas axilares,micropropagacion

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