1,721,254 research outputs found
Agrobacterium rhizogenes rolB and rolD genes: regulation and involvement in plant development
No full textRol genes belong to the T-DNA which is transferred by Agrobacterium rhizogenes into plant cells. Each of these genes affects plant development and is regulated by the host. In this review, after a brief historical background, the most intriguing aspects of past and current research on rolB and rolD genes are highlighted and discussed
Root histogenesis in herbaceous and woody explants cultured in vitro. A critical review
No full textCompetence, determination and root meristemoid organization are key steps in adventitious rooting. A direct and indirect pattern of root formation may be present in both herbaceous and woody systems. The pattern is indirect when competence is achieved during the culture; it is direct when competent cells are present in the tissues at explanting time. Both processes may be activated in the same (herbaceous or woody) explant, and by the same tissue. A coordinated reactivation to division of cell types not directly involved in the rooting process may occur in the woody cuttings. In general, determination occurs before meristemoid formation; however, the ab initio root identity of the meristemoid has been debated. Examples of herbaceous and woody systems showing one or both rooting patterns are described. Studies on mutations affecting the specification of root meristem and on genes involved in cell cycle regulation could contribute to understanding adventitious rooting
Histological analysis of adventitious root formation in Arabidopsis thaliana in planta and in thin cell layers cultured in vitro: the competence of the stem endodermis.
No full textExogenous calcium enhances the formation of vegetative buds, flowers and roots in tobacco pith explants cultured in the absence of exogenous hormones
No full textPith explants excised from the apical stem internodes of vegetative, flowering, and fruiting tobacco plants were cultured on hormone-free medium in the presence or absence of CaCl2 ( 3 mM). The aim was to determine the role of exogenous calcium (Ca2+), applied at the concentration normally present in the Murashige and Skoog ( 1962) medium, in organ formation obtainable in the absence of the exogenous hormonal input. Exclusive formation of vegetative buds was obtained from explants excised from vegetative plants ( pure vegetative programme); vegetative buds and flowers ( and occasionally roots) on the same sample were obtained from explants from flowering plants ( mixed flowering programme); whereas roots, very occasionally associated with vegetative buds and flowers on the same sample, were obtained from explants from fruiting plants ( mixed rooting programme). Histological analysis showed that the organs always exhibited indirect regeneration. Exogenous Ca2+ promoted the formation of meristemoids and the first phases of their growth into organs, but did not change the realization of the organogenic programme and did not affect callogenesis. Instead, the influence of exogenous Ca2+ changed with the programme, when considering the last phases of organ growth (i.e., macroscopic development and elongation), and the appearance of morphological anomalies in the organs
Osmotin induces cold protection in olive trees by affecting programmed cell death and cytoskeleton organization
No full textOsmotin is a pathogenesis-related protein exhibiting cryoprotective functions. Our aim was to understand whether it is involved in the cold acclimation of the olive tree (Olea europaea L.), a frost-sensitive species lacking dormancy. We exposed olive trees expressing tobacco osmotin gene under the 35S promoter (35S:osm) [in the same manner as wild type (wt) plants] to cold shocks in the presence/absence of cold acclimation, and monitored changes in programmed cell death (PCD), cytoskeleton, and calcium ([Ca2+](c)) signalling. In the wt, osmotin was immunolocalized only in cold-acclimated plants, and in the tissues showing PCD. In the 35S:osm clones, the protein was detected also in the non-acclimated plants, and always in the tissues exhibiting PCD. In the non-acclimated wt protoplasts exposed to cold shock, a transient decrease in phallotoxin signal suggests a temporary disassembly of F-actin, a transient increase occurred instead in 35S:osm protoplasts exposed to the same shock. Transient increases in [Ca2+](c) were observed only in the wt protoplasts. However, when F-actin was depolymerized by cytochalasin or latrunculin, and microtubules by colchicine, increase in [Ca2+](c) also occurred in the 35S:osm protoplasts. Successive cold shocks caused transient rises in [Ca2+](c) and transient decreases in the phallotoxin signal in wt protoplasts. No change occurred in [Ca2+](c) occurred in the 35S:osm protoplasts. The phallotoxin signal transiently increased at the first shock, but did not change after the subsequent shocks, and an overall signal reduction occurred with shock repetition. Following acclimation, no cold shock-induced change in [Ca2+](c) levels and F-actin signal occurred either in wt or 35S:osm protoplasts. The results show that osmotin is positively involved in the acclimation-related PCD, in blocking the cold-induced calcium signalling, and in affecting cytoskeleton in response to cold stimuli
Il controllo ormonale dello sviluppo dell'apparato radicale in planta e della rizogenesi in vitro
No full textCalcium involvement in hormone-induced rhizogenesis from thin layers of tobacco and Arabidopsis thaliana
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