RESUMO
An environmentally responsive root system is crucial for plant growth and crop yield, especially in suboptimal soil conditions. This responsiveness enables the plant to exploit regions of high nutrient density while simultaneously minimizing abiotic stress. Despite the vital importance of root systems in regulating plant growth, significant gaps of knowledge exist in the mechanisms that regulate their architecture. Auxin defines both the frequency of lateral root (LR) initiation and the rate of LR outgrowth. Here, we describe a search for proteins that regulate root system architecture (RSA) by interacting directly with a key auxin transporter, PIN1. The native separation of Arabidopsis plasma membrane protein complexes identified several PIN1 co-purifying proteins. Among them, AZG1 was subsequently confirmed as a PIN1 interactor. Here, we show that, in Arabidopsis, AZG1 is a cytokinin (CK) import protein that co-localizes with and stabilizes PIN1, linking auxin and CK transport streams. AZG1 expression in LR primordia is sensitive to NaCl, and the frequency of LRs is AZG1-dependent under salt stress. This report therefore identifies a potential point for auxin:cytokinin crosstalk, which shapes RSA in response to NaCl.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Citocininas , Proteínas de Membrana Transportadoras , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Citocininas/metabolismo , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos/metabolismo , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Raízes de Plantas/metabolismo , Cloreto de SódioRESUMO
To date, synthetic herbicides are the main tools used for weed control, with consequent damage to both the environment and human health. In this respect, searching for new natural molecules and understanding their mode of action could represent an alternative strategy or support to traditional management methods for sustainable agriculture. Protodioscin is a natural molecule belonging to the class of steroid saponins, mainly produced by monocotyledons. In the present paper, protodioscin's phytotoxic potential was assessed to identify its target and the potential mode of action in the model plant Arabidopsis thaliana. The results highlighted that the root system was the main target of protodioscin, which caused a high inhibitory effect on the primary root length (ED50 50 µM) with morphological alteration, accompanied by a significant increase in the lateral root number and root hair density. Through a pharmacological and microscopic approach, it was underlined that this saponin modified both auxin distribution and transport, causing an auxin accumulation in the region of root maturation and an alteration of proteins responsible for the auxin efflux (PIN2). In conclusion, the saponin protodioscin can modulate the root system of A. thaliana by interfering with the auxin transport (PAT).
RESUMO
Adventitious roots (ARs) form from above-ground organs, and auxins are major regulators of AR development. TIR1/AFB F-box proteins act as well-established auxin receptors. Auxin transport involves the PINFORMED (PIN) auxin efflux carriers and AUXIN RESISTANT 1/LIKE AUX1 (AUX1/LAX1) influx carriers. To further elucidate the basis of AR development, we investigated the participation of these proteins and phosphorylation of PINs during adventitious rooting in hypocotyls of pre-etiolated flooded Arabidopsis thaliana seedlings. Mutant and GUS localization studies indicated that AFB2 is important in AR development. AUX1 loss-of-function reduced AR numbers, which could not be reversed by exogenous auxin. Single mutations in LAX1, LAX2 and LAX3 had no negative impact on AR development and the first and last mutations even promoted it. Double and triple mutants of AUX1, LAX1, LAX2 and LAX3 significantly reduced rooting, which was reversed by exogenous auxin. AUX1 was essential in AR establishment, with LAX3 apparently acting in conjunction. Proper phosphorylation of PINs by PID, WAG1 and WAG2 and auxin transport direction were equally essential for AR establishment. PIN1, AUX1 and AFB2 (overexpression) and LAX1, LAX3, PIN4 and PIN7 (downregulation) emerged as potential targets for genetic manipulation aiming at improving AR development.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Inundações , Ácidos Indolacéticos/metabolismo , Proteínas de Plantas/metabolismo , Receptores de Superfície Celular/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Transporte Biológico , Estiolamento , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Plântula/genética , Plântula/crescimento & desenvolvimentoRESUMO
Auxins are plant growth regulators that participate in a variety of biological mechanisms during the growth and development of plants. The most abundant natural auxin is indole-3-acetic acid (IAA). The physiological processes regulated by IAA depend on their temporal space accumulation in different tissues of a plant. This accumulation is regulated by its biosynthesis, conjugation, degradation, and transport. Therefore tools that allow us a qualitative and quantitative detection of IAA in plant tissues are very useful to understand the homeostasis of IAA during the life cycle of plants. In this protocol, the complete procedure for localization of IAA in different tissues of Coffea canephora is described using specific anti-IAA monoclonal antibodies.
Assuntos
Coffea/metabolismo , Imuno-Histoquímica/métodos , Ácidos Indolacéticos/metabolismo , Especificidade de Órgãos , Coffea/genética , Dessecação , Genes de Plantas , Família Multigênica , Filogenia , Inclusão do Tecido , Fixação de TecidosRESUMO
High-resolution and automated image analysis of individual roots demonstrated that endogenous nitric oxide (NO) contribute significantly to gravitropism of Arabidopsis roots. Lowering of endogenous NO concentrations strongly reduced and even reversed gravitropism, resulting in upward bending, without affecting root growth rate. Notably, the asymmetric accumulation of NO along the upper and lower sides of roots correlated with a positive gravitropic response. Detection of NO by the specific DAF-FM DA fluorescent probe revealed that NO was higher at the lower side of horizontally-oriented roots returning to initial values 2 h after the onset of gravistimulation. We demonstrate that NO promotes plasma membrane re-localization of PIN2 in epidermal cells, which is required during the early root gravitropic response. The dynamic and asymmetric localization of both auxin and NO is critical to regulate auxin polar transport during gravitropism. Our results collectively suggest that, although auxin and NO crosstalk occurs at different levels of regulation, they converge in the regulation of PIN2 membrane trafficking in gravistimulated roots, supporting the notion that a temporally and spatially coordinated network of signal molecules could participate in the early phases of auxin polar transport during gravitropism.
RESUMO
Auxin and polar auxin transport have been implicated in controlling zygotic embryo development, but less is known about their role in the development of somatic embryos. The aim of this study was to determine if indole-3-acetic acid (IAA) and the PIN1 transporter participate in the induction of somatic embryogenesis (SE) and the development of somatic embryos. The results show that IAA levels gradually increase during pre-treatment and accumulate in the chloroplast. During pre-treatment and the globular stage of SE in C. canephora, auxin is distributed uniformly in all of the cells of the somatic embryo. During the subsequent stages of development, auxins are mobilized to the cells that will form the cotyledons and the root meristem. The location of the PIN transporters shifts from the plasmalemma of the protoderm cells during the globular stage to the plasmalemma of the cells that will give rise to the cotyledons and the vascular tissue in the late stages of somatic embryogenesis. The incubation of the explants in the presence of 2,3,5-triiodobenzoic acid (TIBA) produced aberrant somatic embryos, suggesting that PIN1 mediates the transport of IAA.
Assuntos
Coffea/metabolismo , Ácidos Indolacéticos/metabolismo , Técnicas de Embriogênese Somática de Plantas , Transporte Biológico/efeitos dos fármacos , Coffea/citologia , Coffea/embriologia , Coffea/crescimento & desenvolvimento , Espaço Intracelular/metabolismo , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Proteínas de Plantas/metabolismo , Ácidos Tri-Iodobenzoicos/farmacologiaRESUMO
Coordinated cell polarization in developing tissues is a recurrent theme in multicellular organisms. In plants, a directional distribution of the plant hormone auxin is at the core of many developmental programs. A feedback regulation of auxin on the polarized localization of PIN auxin transporters in individual cells has been proposed as a self-organizing mechanism for coordinated tissue polarization, but the molecular mechanisms linking auxin signalling to PIN-dependent auxin transport remain unknown. We used a microarray-based approach to find regulators of the auxin-induced PIN relocation in Arabidopsis thaliana root, and identified a subset of a family of phosphatidylinositol transfer proteins (PITPs), the PATELLINs (PATLs). Here, we show that PATLs are expressed in partially overlapping cell types in different tissues going through mitosis or initiating differentiation programs. PATLs are plasma membrane-associated proteins accumulated in Arabidopsis embryos, primary roots, lateral root primordia and developing stomata. Higher order patl mutants display reduced PIN1 repolarization in response to auxin, shorter root apical meristem, and drastic defects in embryo and seedling development. This suggests that PATLs play a redundant and crucial role in polarity and patterning in Arabidopsis.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Desenvolvimento Vegetal , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Padronização Corporal/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Ácidos Indolacéticos/farmacologia , Proteínas de Membrana Transportadoras/genética , Mutação/genética , Fenótipo , Filogenia , Desenvolvimento Vegetal/efeitos dos fármacos , Epiderme Vegetal/citologia , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Plântula/efeitos dos fármacos , Plântula/metabolismo , Sementes/efeitos dos fármacos , Sementes/genéticaRESUMO
BACKGROUND: Indole-3-acetic acid (IAA), the most abundant auxin, is a growth promoter hormone involved in several developmental processes. Auxin homeostasis is very important to its function and this is achieved through the regulation of IAA biosynthesis, conjugation, degradation and transport. In grapevine, IAA plays an essential role during initial stages of berry development, since it delays fruitlet abscission by reducing the ethylene sensitivity in the abscission zone. For this reason, Continuous polar IAA transport to the pedicel is required. This kind of transport is controlled by IAA, which regulates its own movement by modifying the expression and localization of PIN-FORMED (PIN) auxin efflux facilitators that localize asymmetrically within the cell. On the other hand, the hormone gibberellin (GA) also activates the polar auxin transport by increasing PIN stability. In Vitis vinifera, fruitlet abscission occurs during the first two to three weeks after flowering. During this time, IAA and GA are present, however the role of these hormones in the control of polar auxin transport is unknown. RESULTS: In this work, the use of radiolabeled IAA showed that auxin is basipetally transported during grapevine fruitlet abscission. This observation was further supported by immunolocalization of putative VvPIN proteins that display a basipetal distribution in pericarp cells. Polar auxin transport and transcripts of four putative VvPIN genes decreased in conjunction with increased abscission, and the inhibition of polar auxin transport resulted in fruit drop. GA3 and IAA treatments reduced polar auxin transport, but only GA3 treatment decreased VvPIN transcript abundance. When GA biosynthesis was blocked, IAA was capable to increase polar auxin transport, suggesting that its effect depends on GA content. Finally, we observed significant changes in the content of several IAA-related compounds during the abscission period. CONCLUSIONS: These results provide evidence that auxin homeostasis plays a central role during grapevine initial fruit development and that GA and IAA controls auxin homeostasis by reducing polar auxin transport.