RESUMO
CLE peptides are involved in the balance between cell division and differentiation throughout plant development, including nodulation. Previously, two CLE genes of Medicago truncatula, MtCLE12 and MtCLE13, had been identified whose expression correlated with nodule primordium formation and meristem establishment. Gain-of-function analysis indicated that both MtCLE12 and MtCLE13 interact with the SUPER NUMERIC NODULES (SUNN)-dependent auto-regulation of nodulation to control nodule numbers. Here we demonstrate that cytokinin, which is essential for nodule organ formation, regulates MtCLE13 expression. In addition, simultaneous knockdown of MtCLE12 and MtCLE13 resulted in an increase in nodule number, implying that both genes play a role in controlling nodule number. Additionally, a weak link may exist with the ethylene-dependent mechanism that locally controls nodule number.
Assuntos
Citocininas/farmacologia , Medicago truncatula/genética , Peptídeos/genética , Reguladores de Crescimento de Plantas/farmacologia , Proteínas de Plantas/genética , Nodulação/genética , Diferenciação Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Etilenos/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/genética , Técnicas de Silenciamento de Genes , Medicago truncatula/efeitos dos fármacos , Medicago truncatula/microbiologia , Medicago truncatula/fisiologia , Modelos Biológicos , Mutação , Peptídeos/metabolismo , Proteínas de Plantas/metabolismo , Nodulação/efeitos dos fármacos , Plantas Geneticamente Modificadas , Nódulos Radiculares de Plantas/efeitos dos fármacos , Nódulos Radiculares de Plantas/genética , Nódulos Radiculares de Plantas/crescimento & desenvolvimento , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Sinorhizobium meliloti/efeitos dos fármacos , Sinorhizobium meliloti/fisiologia , SimbioseRESUMO
⢠Legume roots develop two types of lateral organs, lateral roots and nodules. Nodules develop as a result of a symbiotic interaction with rhizobia and provide a niche for the bacteria to fix atmospheric nitrogen for the plant. ⢠The Arabidopsis NAC1 transcription factor is involved in lateral root formation, and is regulated post-transcriptionally by miRNA164 and by SINAT5-dependent ubiquitination. We analyzed in Medicago truncatula the role of the closest NAC1 homolog in lateral root formation and in nodulation. ⢠MtNAC1 shows a different expression pattern in response to auxin than its Arabidopsis homolog and no changes in lateral root number or nodulation were observed in plants affected in MtNAC1 expression. In addition, no interaction was found with SINA E3 ligases, suggesting that post-translational regulation of MtNAC1 does not occur in M. truncatula. Similar to what was found in Arabidopsis, a conserved miR164 target site was retrieved in MtNAC1, which reduced protein accumulation of a GFP-miR164 sensor. Furthermore, miR164 and MtNAC1 show an overlapping expression pattern in symbiotic nodules, and overexpression of this miRNA led to a reduction in nodule number. ⢠This work suggests that regulatory pathways controlling a conserved transcription factor are complex and divergent between M. truncatula and Arabidopsis.
Assuntos
Medicago truncatula/fisiologia , Proteínas de Plantas/metabolismo , Sinorhizobium meliloti/fisiologia , Fatores de Transcrição/metabolismo , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Sequência de Bases , Flores/efeitos dos fármacos , Flores/genética , Flores/fisiologia , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos/farmacologia , Medicago truncatula/efeitos dos fármacos , Medicago truncatula/genética , MicroRNAs/genética , Dados de Sequência Molecular , Mutação , Filogenia , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/genética , Folhas de Planta/fisiologia , Proteínas de Plantas/química , Proteínas de Plantas/genética , Nodulação/genética , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/genética , Raízes de Plantas/fisiologia , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/genética , Brotos de Planta/fisiologia , Plantas Geneticamente Modificadas/efeitos dos fármacos , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/fisiologia , Estrutura Terciária de Proteína , RNA de Plantas/genética , Proteínas Recombinantes de Fusão , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Nicotiana/genética , Nicotiana/metabolismo , Transativadores/genética , Transativadores/metabolismo , Fatores de Transcrição/química , Fatores de Transcrição/genéticaRESUMO
CLE peptides are potentially involved in nodule organ development and in the autoregulation of nodulation (AON), a systemic process that restricts nodule number. A genome-wide survey of CLE peptide genes in the soybean glycine max genome resulted in the identification of 39 GmCLE genes, the majority of which have not yet been annotated. qRT-PCR analysis indicated two different nodulation-related CLE expression patterns, one linked with nodule primordium development and a new one linked with nodule maturation. Moreover, two GmCLE gene pairs, encoding group-III CLE peptides that were previously shown to be involved in AON, had a transient expression pattern during nodule development, were induced by the essential nodulation hormone cytokinin, and one pair was also slightly induced by the addition of nitrate. Hence, our data support the hypothesis that group-III CLE peptides produced in the nodules are involved in primordium homeostasis and intertwined in activating AON, but not in sustaining it.
Assuntos
Genes de Plantas/genética , Glycine max/genética , Nodulação/genética , Diferenciação Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Biologia Computacional , Citocininas/farmacologia , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Ácidos Indolacéticos/farmacologia , Nitratos/farmacologia , Especificidade de Órgãos/efeitos dos fármacos , Especificidade de Órgãos/genética , Peptídeos/genética , Filogenia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Nodulação/efeitos dos fármacos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Nódulos Radiculares de Plantas/citologia , Nódulos Radiculares de Plantas/efeitos dos fármacos , Nódulos Radiculares de Plantas/genética , Nódulos Radiculares de Plantas/crescimento & desenvolvimento , Glycine max/citologia , Glycine max/efeitos dos fármacos , Glycine max/crescimento & desenvolvimentoRESUMO
The CLAVATA3/embryo-surrounding region (CLE) peptides control the fine balance between proliferation and differentiation in plant development. We studied the role of CLE peptides during indeterminate nodule development and identified 25 MtCLE peptide genes in the Medicago truncatula genome, of which two genes, MtCLE12 and MtCLE13, had nodulation-related expression patterns that were linked to proliferation and differentiation. MtCLE13 expression was up-regulated early in nodule development. A high-to-low expression gradient radiated from the inner toward the outer cortical cell layers in a region defining the incipient nodule. At later stages, MtCLE12 and MtCLE13 were expressed in differentiating nodules and in the apical part of mature, elongated nodules. Functional analysis revealed a putative role for MtCLE12 and MtCLE13 in autoregulation of nodulation, a mechanism that controls the number of nodules and involves systemic signals mediated by a leucine-rich repeat receptor-like kinase, SUNN, which is active in the shoot. When MtCLE12 and MtCLE13 were ectopically expressed in transgenic roots, nodulation was abolished at the level of the nodulation factor signal transduction, and this inhibition involved long-distance signaling. In addition, composite plants with roots ectopically expressing MtCLE12 or MtCLE13 had elongated petioles. This systemic effect was not observed in transgenic roots ectopically expressing MtCLE12 and MtCLE13 in a sunn-1 mutant background, although nodulation was still strongly reduced. These results suggest multiple roles for CLE signaling in nodulation.