RESUMO
Auxin plays a dual role in growth regulation and, depending on the tissue and concentration of the hormone, it can either promote or inhibit division and expansion processes in plants. Recent studies have revealed that, beyond transcriptional reprogramming, alternative auxin-controlled mechanisms regulate root growth. Here, we explored the impact of different concentrations of the synthetic auxin NAA that establish growth-promoting and -repressing conditions on the root tip proteome and phosphoproteome, generating a unique resource. From the phosphoproteome data, we pinpointed (novel) growth regulators, such as the RALF34-THE1 module. Our results, together with previously published studies, suggest that auxin, H+-ATPases, cell wall modifications and cell wall sensing receptor-like kinases are tightly embedded in a pathway regulating cell elongation. Furthermore, our study assigned a novel role to MKK2 as a regulator of primary root growth and a (potential) regulator of auxin biosynthesis and signalling, and suggests the importance of the MKK2 Thr31 phosphorylation site for growth regulation in the Arabidopsis root tip.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Hormônios Peptídicos/genética , Fosfoproteínas/genética , Reguladores de Crescimento de Plantas/farmacologia , Raízes de Plantas/genética , Proteínas Quinases/genética , Receptores de Superfície Celular/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Ácidos Indolacéticos/farmacologia , Meristema/genética , Meristema/crescimento & desenvolvimento , Meristema/metabolismo , Quinases de Proteína Quinase Ativadas por Mitógeno/genética , Quinases de Proteína Quinase Ativadas por Mitógeno/metabolismo , Ácidos Naftalenoacéticos/síntese química , Ácidos Naftalenoacéticos/farmacologia , Hormônios Peptídicos/metabolismo , Fosfoproteínas/classificação , Fosfoproteínas/metabolismo , Fosforilação , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Proteínas Quinases/metabolismo , Processamento de Proteína Pós-Traducional , Proteoma/classificação , Proteoma/genética , Proteoma/metabolismo , ATPases Translocadoras de Prótons/genética , ATPases Translocadoras de Prótons/metabolismo , Receptores de Superfície Celular/metabolismo , Transdução de SinaisRESUMO
The plant root cap, surrounding the very tip of the growing root, perceives and transmits environmental signals to the inner root tissues. In Arabidopsis thaliana, auxin released by the root cap contributes to the regular spacing of lateral organs along the primary root axis. Here, we show that the periodicity of lateral organ induction is driven by recurrent programmed cell death at the most distal edge of the root cap. We suggest that synchronous bursts of cell death in lateral root cap cells release pulses of auxin to surrounding root tissues, establishing the pattern for lateral root formation. The dynamics of root cap turnover may therefore coordinate primary root growth with root branching in order to optimize the uptake of water and nutrients from the soil.
Assuntos
Apoptose , Arabidopsis/crescimento & desenvolvimento , Ácidos Indolacéticos/metabolismo , Coifa/crescimento & desenvolvimento , Arabidopsis/citologia , Arabidopsis/metabolismo , Epiderme Vegetal/citologia , Epiderme Vegetal/crescimento & desenvolvimento , Epiderme Vegetal/metabolismo , Coifa/citologia , Coifa/metabolismo , Receptores do Ligante Indutor de Apoptose Relacionado a TNF/genética , Receptores do Ligante Indutor de Apoptose Relacionado a TNF/metabolismo , Transdução de Sinais , Solo , Água/metabolismoRESUMO
During the exploration of the soil by plant roots, uptake of water and nutrients can be greatly fostered by a regular spacing of lateral roots (LRs). In the Arabidopsis root, a regular branching pattern depends on oscillatory gene activity to create prebranch sites, patches of cells competent to form LRs. Thus far, the molecular components regulating the oscillations still remain unclear. Here, we show that a local auxin source in the root cap, derived from the auxin precursor indole-3-butyric acid (IBA), modulates the oscillation amplitude, which in turn determines whether a prebranch site is created or not. Moreover, transcriptome profiling identified novel and IBA-regulated components of root patterning, such as the MEMBRANE-ASSOCIATED KINASE REGULATOR4 (MAKR4) that converts the prebranch sites into a regular spacing of lateral organs. Thus, the spatiotemporal patterning of roots is fine-tuned by the root cap-specific conversion pathway of IBA to auxin and the subsequent induction of MAKR4.