RESUMEN
Directional transport of the phytohormone auxin is a versatile, plant-specific mechanism regulating many aspects of plant development. The recently identified plant hormones, strigolactones (SLs), are implicated in many plant traits; among others, they modify the phenotypic output of PIN-FORMED (PIN) auxin transporters for fine-tuning of growth and developmental responses. Here, we show in pea and Arabidopsis that SLs target processes dependent on the canalization of auxin flow, which involves auxin feedback on PIN subcellular distribution. D14 receptor- and MAX2 F-box-mediated SL signaling inhibits the formation of auxin-conducting channels after wounding or from artificial auxin sources, during vasculature de novo formation and regeneration. At the cellular level, SLs interfere with auxin effects on PIN polar targeting, constitutive PIN trafficking as well as clathrin-mediated endocytosis. Our results identify a non-transcriptional mechanism of SL action, uncoupling auxin feedback on PIN polarity and trafficking, thereby regulating vascular tissue formation and regeneration.
Asunto(s)
Compuestos Heterocíclicos con 3 Anillos/metabolismo , Ácidos Indolacéticos/metabolismo , Lactonas/metabolismo , Pisum sativum/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Regulación de la Expresión Génica de las Plantas/genética , Regulación de la Expresión Génica de las Plantas/fisiología , Pisum sativum/genética , Reguladores del Crecimiento de las Plantas/metabolismoRESUMEN
Apical dominance is one of the fundamental developmental phenomena in plant biology, which determines the overall architecture of aerial plant parts. Here we show apex decapitation activated competition for dominance in adjacent upper and lower axillary buds. A two-nodal-bud pea (Pisum sativum L.) was used as a model system to monitor and assess auxin flow, auxin transport channels, and dormancy and initiation status of axillary buds. Auxin flow was manipulated by lateral stem wounds or chemically by auxin efflux inhibitors 2,3,5-triiodobenzoic acid (TIBA), 1-N-naphtylphtalamic acid (NPA), or protein synthesis inhibitor cycloheximide (CHX) treatments, which served to interfere with axillary bud competition. Redirecting auxin flow to different points influenced which bud formed the outgrowing and dominant shoot. The obtained results proved that competition between upper and lower axillary buds as secondary auxin sources is based on the same auxin canalization principle that operates between the shoot apex and axillary bud.
Asunto(s)
Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Ácidos Indolacéticos/farmacología , Pisum sativum/crecimiento & desarrollo , Reguladores del Crecimiento de las Plantas/farmacología , Proteínas de Plantas/genética , Brotes de la Planta/crecimiento & desarrollo , Tallos de la Planta/crecimiento & desarrollo , Transporte Biológico , Pisum sativum/efectos de los fármacos , Pisum sativum/genética , Brotes de la Planta/efectos de los fármacos , Brotes de la Planta/genética , Tallos de la Planta/efectos de los fármacos , Tallos de la Planta/genéticaRESUMEN
Shoot branching is one of the major determinants of plant architecture. Polar auxin transport in stems is necessary for the control of bud outgrowth by a dominant apex. Here, we show that following decapitation in pea (Pisum sativum L.), the axillary buds establish directional auxin export by subcellular polarization of PIN auxin transporters. Apical auxin application on the decapitated stem prevents this PIN polarization and canalization of laterally applied auxin. These results support a model in which the apical and lateral auxin sources compete for primary channels of auxin transport in the stem to control the outgrowth of axillary buds.
Asunto(s)
Ácidos Indolacéticos/metabolismo , Pisum sativum/crecimiento & desarrollo , Reguladores del Crecimiento de las Plantas/metabolismo , Proteínas de Plantas/metabolismo , Tallos de la Planta/metabolismo , Regulación de la Expresión Génica de las Plantas , Pisum sativum/genética , Pisum sativum/metabolismo , Proteínas de Plantas/genética , Tallos de la Planta/crecimiento & desarrolloRESUMEN
The effects of isopentenyladenosine (iPA) on tobacco (Nicotiana tabacum L.) BY-2 cells were examined. The number of BY-2 cells decreased in a time- and concentration-dependent manner after being exposed to micromolar concentrations of iPA. This decrease was mainly due to a loss of cell viability, since no substantial changes in cell cycle progression were revealed by flow-cytometric analysis. Dying cells exhibited the typical morphological and biochemical hallmarks of apoptosis, including cell shrinkage, chromatin condensation, and degradation of nuclear DNA to nucleosomal size fragments. Caspase-1-like and caspase-3-like proteases also became activated, the former being dominant. Inhibitor-sensitivity studies revealed that although synthetic caspase inhibitors failed to prevent cell death they markedly reduced cell death in tobacco BY-2 cells, Nu-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone, a specific inhibitor for caspase-1, being the most effective. Our results indicate that caspase-like proteases, and particularly caspase-1-like protease, might be critically implicated in iPA-induced apoptosis of BY-2 cells. Finally, the outcome of inhibiting adenosine kinase by 4-amino-3-iodo-1(beta- D-ribofuranosyl)pyrazolo[3,4-d]-pyrimidine revealed that intracellular phosphorylation of iPA is required for its cytotoxicity to develop.
