RESUMEN

The interactions of legumes with symbiotic nitrogen-fixing bacteria cause the formation of specialized lateral root organs called root nodules. It has been postulated that this root nodule symbiosis system has recruited factors that act in early signaling pathways (common SYM genes) partly from the ancestral mycorrhizal symbiosis. However, the origins of factors needed for root nodule organogenesis are largely unknown. NODULE INCEPTION (NIN) is a nodulation-specific gene that encodes a putative transcription factor and acts downstream of the common SYM genes. Here, we identified two Nuclear Factor-Y (NF-Y) subunit genes, LjNF-YA1 and LjNF-YB1, as transcriptional targets of NIN in Lotus japonicus. These genes are expressed in root nodule primordia and their translational products interact in plant cells, indicating that they form an NF-Y complex in root nodule primordia. The knockdown of LjNF-YA1 inhibited root nodule organogenesis, as did the loss of function of NIN. Furthermore, we found that NIN overexpression induced root nodule primordium-like structures that originated from cortical cells in the absence of bacterial symbionts. Thus, NIN is a crucial factor responsible for initiating nodulation-specific symbiotic processes. In addition, ectopic expression of either NIN or the NF-Y subunit genes caused abnormal cell division during lateral root development. This indicated that the Lotus NF-Y subunits can function to stimulate cell division. Thus, transcriptional regulation by NIN, including the activation of the NF-Y subunit genes, induces cortical cell division, which is an initial step in root nodule organogenesis. Unlike the legume-specific NIN protein, NF-Y is a major CCAAT box binding protein complex that is widespread among eukaryotes. We propose that the evolution of root nodules in legume plants was associated with changes in the function of NIN. NIN has acquired functions that allow it to divert pathways involved in the regulation of cell division to root nodule organogenesis.

Asunto(s)

Factor de Unión a CCAAT/genética , Proteínas de Plantas , Nódulos de las Raíces de las Plantas , Simbiosis/genética , Evolución Biológica , Factor de Unión a CCAAT/metabolismo , Fabaceae/genética , Fabaceae/metabolismo , Regulación de la Expresión Génica de las Plantas , Lotus/genética , Lotus/crecimiento & desarrollo , Organogénesis , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Nódulos de las Raíces de las Plantas/genética , Nódulos de las Raíces de las Plantas/crecimiento & desarrollo , Nódulos de las Raíces de las Plantas/metabolismo , Nódulos de las Raíces de las Plantas/microbiología , Transducción de Señal , Factores de Transcripción

RESUMEN

At the onset of flowering, the Arabidopsis thaliana primary inflorescence meristem starts to produce flower meristems on its flank. Determination of floral fate is associated with changes in the growth pattern and expression of meristem identity genes and suppression of a subtending leaf called a bract. Here, we show a role in floral fate determination and bract suppression for the PUCHI gene, an AP2/EREBP family gene that has previously been reported to play roles in lateral root morphogenesis. Mutations in PUCHI cause partial conversion of flowers to inflorescences, indicating that PUCHI is required for flower meristem identity. PUCHI is transiently expressed in the early flower meristem and accelerates meristem bulging while it prevents the growth of the bract primordium. The function of PUCHI in floral fate determination and bract suppression overlaps that of the BLADE-ON-PETIOLE1 (BOP1) and BOP2 genes, which encode a pair of redundant regulatory proteins involved in various developmental processes, including leaf morphogenesis and flower patterning. We also show that PUCHI acts together with BOP1 and BOP2 to promote expression of LEAFY and APETALA1, two central regulators of floral meristem identity. Expression patterns of the PUCHI and BOP genes point to a role in spatial control of flower-specific activation of these meristem identity genes.

Asunto(s)

Proteínas de Arabidopsis/fisiología , Arabidopsis/crecimiento & desarrollo , Meristema/citología , Factores de Transcripción/fisiología , Arabidopsis/citología , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Diferenciación Celular/genética , Flores/citología , Flores/genética , Flores/crecimiento & desarrollo , Proteínas de Dominio MADS/genética , Proteínas de Dominio MADS/metabolismo , Meristema/genética , Meristema/crecimiento & desarrollo , Modelos Biológicos , Datos de Secuencia Molecular , Factores de Transcripción/genética , Factores de Transcripción/metabolismo

RESUMEN

Organ primordia develop from founder cells into organs due to coordinated patterns of cell division. How patterned cell division is regulated during organ formation, however, is not well understood. Here, we show that the PUCHI gene, which encodes a putative APETALA2/ethylene-responsive element binding protein transcription factor, is required for the coordinated pattern of cell divisions during lateral root formation in Arabidopsis thaliana. Recessive mutations in PUCHI disturbed cell division patterns in the lateral root primordium, resulting in swelling of the proximal region of lateral roots. PUCHI expression was initially detected in all of the cells in early lateral root primordia, and later it was restricted to the proximal region of the primordia. Stable expression of PUCHI required auxin-responsive elements in its promoter region, and exogenous auxin increased the level of PUCHI mRNA accumulation. These results suggest that PUCHI acts downstream of auxin signaling and that this gene contributes to lateral root morphogenesis through affecting the pattern of cell divisions during the early stages of primordium development.

Asunto(s)

Proteínas de Arabidopsis/genética , Arabidopsis/embriología , Proteínas de Unión al ADN/metabolismo , Proteínas de Homeodominio/metabolismo , Ácidos Indolacéticos/metabolismo , Morfogénesis , Proteínas Nucleares/metabolismo , Proteínas de Plantas/metabolismo , Raíces de Plantas/embriología , Factores de Transcripción/genética , Secuencia de Aminoácidos , Arabidopsis/efectos de los fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Secuencia de Bases , Clonación Molecular , Flores/efectos de los fármacos , Flores/crecimiento & desarrollo , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Genes de Plantas , Glucuronidasa/metabolismo , Proteínas Fluorescentes Verdes/metabolismo , Ácidos Indolacéticos/farmacología , Modelos Biológicos , Datos de Secuencia Molecular , Morfogénesis/efectos de los fármacos , Mutación/genética , Fenotipo , Raíces de Plantas/citología , Raíces de Plantas/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Factores de Transcripción/química , Factores de Transcripción/metabolismo

RESUMEN

Gene expression profiles during early stages of formation of symbiotic nitrogen-fixing nodules in a model legume Lotus japonicus were analyzed by means of a cDNA array of 18,144 non-redundant expressed sequence tags (ESTs) isolated from L. japonicus. Expression of a total of 1,076 genes was significantly accelerated during the successive stages that represent infection of Mesorhizobium loti, nodule primordium initiation, nodule organogenesis, and the onset of nitrogen fixation. These include 32 nodulin and nodulinhomolog genes as well as a number of genes involved in the catabolism of photosynthates and assimilation of fixed nitrogen that were previously known to be abundantly expressed in root nodules of many legumes. We also identified a large number of novel nodule-specific or enhanced genes, which include genes involved in many cellular processes such as membrane transport, defense responses, phytohormone synthesis and responses, signal transduction, cell wall synthesis, and transcriptional regulation. Notably, our data indicate that the gene expression profile in early steps of Rhizobium-legume interactions is considerably different from that in subsequent stages of nodule development. A number of genes involved in the defense responses to pathogens and other stresses were induced abundantly in the infection process, but their expression was suppressed during subsequent nodule formation. The results provide a comprehensive data source for investigation of molecular mechanisms underlying nodulation and symbiotic nitrogen fixation.

Asunto(s)

Perfilación de la Expresión Génica , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Genes Bacterianos , Lotus/genética , Fijación del Nitrógeno/genética , Northern Blotting , Pared Celular/metabolismo , ADN Complementario/genética , Etiquetas de Secuencia Expresada , Lotus/citología , Lotus/crecimiento & desarrollo , Proteínas de la Membrana/genética , Análisis de Secuencia por Matrices de Oligonucleótidos , Reguladores del Crecimiento de las Plantas/biosíntesis , Proteínas de Plantas/genética , Raíces de Plantas/metabolismo , Reacción en Cadena de la Polimerasa , ARN de Planta/genética , Rhizobiaceae/fisiología , Transducción de Señal/genética , Simbiosis , Transcripción Genética/genética

RESUMEN

The fermentation product of herbs by lactic acid bacteria (FHL) was assayed for antifungal activities against Rosellinia necatrix, Helicobasidium mompa, Fusarium oxysporum, Pythium graminicola and Pyricularia oryzae. FHL completely inhibited the growth of R. necatrix, H. mompa, P. graminicola and P. oryzae, and reduced the growth of F. oxysporum by 35%. When the seeds of Medicago sativa L. (alfalfa), Asparagus officinalis L. (asparagus), Brassica campestris L. (komatsuna), Oryza sativa L. (rice), Spinacia oleracea L. (spinach), Festuca arundinacea Schreb. (tall fescue), and Lycopersicum esculentum Mill. (tomato) were put on plates containing 0.69 mg/ml FHL, their germination rates did not decrease. The root elongation of A. officinalis, B. campestris, O. sativa, and L. esculentum seedlings was suppressed on plates containing 6.92 mg/ml FHL, but the root elongation of M. sativa was not suppressed on the 6.92 mg/ml FHL plate. When FHL was diluted to less than 1.73 mg/ml, the diluted FHL solution did not suppress the germination of B. campestris seeds, but it suppressed the root elongation of B. campestris seedlings. An FHL concentration higher than 0.35 mg/ml hastened the growth of seedlings of B. campestris in the presence of a chemical fertilizer but delayed the growth of these seedlings in the absence of the chemical fertilizer, suggesting that inorganic elements could affect the efficiency of FHL.