RESUMEN
The development of floral organs is coordinated by an elaborate network of homeotic genes, and gibberellin (GA) signaling is involved in floral organ development; however, the underlying molecular mechanisms remain elusive. In the present study, we found that MOS4-ASSOCIATED COMPLEX 5A (MAC5A), which is a protein containing an RNA-binding motif, was involved in the development of sepals, petals, and stamens; either the loss or gain of MAC5A function resulted in stamen malformation and a reduced seed set. The exogenous application of GA considerably exacerbated the defects in mac5a null mutants, including fewer stamens and male sterility. MAC5A was predominantly expressed in pollen grains and stamens, and overexpression of MAC5A affected the expression of homeotic genes such as APETALA1 (AP1), AP2, and AGAMOUS (AG). MAC5A may interact with RABBIT EARS (RBE), a repressor of AG expression in Arabidopsis flowers. The petal defect in rbe null mutants was at least partly rescued in mac5a rbe double mutants. These findings suggest that MAC5A is a novel factor that is required for the normal development of stamens and depends on the GA signaling pathway.
Asunto(s)
Flores/efectos de los fármacos , Giberelinas/farmacología , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Flores/genética , Flores/metabolismo , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Genes Homeobox/efectos de los fármacos , Genes Homeobox/genética , Genes de Plantas/efectos de los fármacos , Genes de Plantas/genética , Morfogénesis/efectos de los fármacos , Morfogénesis/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Polen/efectos de los fármacos , Polen/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
Pollen wall characteristics are dramatically changed during pollen maturation. Many genes have been identified as regulators of such changes in pollen wall characteristics, but mechanisms of such changes have not been completely understood. Here, a GDSL-type esterase/lipase gene, GELP77, is shown to regulate such changes in Arabidopsis thaliana. GELP77-deficient (gelp77) plants exhibited male sterility, and this phenotype was suppressed by introduction of a GELP77 genomic fragment. Mature pollen grains of wild-type Arabidopsis plants have an organized reticulate surface structure and are dissociated from each other. In contrast, pollen grains of gelp77 lacked such a structure and were shrunken and stuck to each other. Nuclei were not detectable in gelp77 microspores at a putative uninucleate stage, suggesting that GELP77 is required as early as this stage. In plants that have the GELP77 promoter-GELP77-GFP transgene, the GELP77-GFP fusion protein was detected in microspores, tapetal cells and middle layer cells in anthers at post-meiotic stages, whereas not anthers at pre-meiotic stages. Analysis of amino acid sequences suggests that GELP77 is phylogenetically distant from the other 104 GDSL-type esterase/lipase genes in Arabidopsis and that GELP77 orthologs are present in various plant species. Together, these results indicate that GELP77 regulates pollen wall characteristics in Arabidopsis.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Arabidopsis/fisiología , Hidrolasas de Éster Carboxílico/metabolismo , Genes de Plantas , Lipasa/genética , Polen/fisiología , Arabidopsis/ultraestructura , Proteínas de Arabidopsis/genética , Hidrolasas de Éster Carboxílico/genética , Secuencia Conservada/genética , Fertilidad/fisiología , Regulación de la Expresión Génica de las Plantas , Técnicas de Inactivación de Genes , Lipasa/metabolismo , Filogenia , Infertilidad Vegetal/genética , Polen/ultraestructura , Vías SecretorasRESUMEN
Protein phosphatase 2A (PP2A) is a heterotrimeric protein complex conserved among eukaryotes. The B subunit of PP2A determines the substrate specificity of the PP2A holoenzyme, and is classified into the B, B', Bâ³ and Bâ´ families. Arabidopsis thaliana has two isoforms of the B-family subunit (ATBA and ATBB). A double knockout of their genes is lethal, but which developmental process is primarily impaired by the double knockout is unclear. Identifying such a process helps understand PP2A-mediated signaling more deeply. Here, genetic characterization of new knockout mutants for these genes shows that they are necessary for pollen development but not for female gametophyte development. Compared to wild-type pollen grains, the mutant pollen grains exhibited lower enzyme activities, germinated less frequently on stigmas, and exhibited the aberrant numbers of sperm cell nuclei, suggesting that ATBA and ATBB play pleiotropic roles in pollen development. The amino acids stabilizing the interaction between the human PP2A A and B-family subunits are conserved in an Arabidopsis A subunit (AtPP2AA2), ATBA and ATBB. His-tagged AtPP2AA2 co-immunoprecipitated with either Myc-tagged ATBA or Myc-tagged ATBB in vitro, confirming their interactions. Proteins that regulate pollen development and that undergo dephosphorylation are likely primary targets of ATBA and ATBB.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Isoenzimas/metabolismo , Óvulo Vegetal/metabolismo , Polen/metabolismo , Proteína Fosfatasa 2/metabolismo , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Proteínas de Arabidopsis/genética , Flores/genética , Flores/crecimiento & desarrollo , Flores/metabolismo , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Isoenzimas/genética , Mutación , Óvulo Vegetal/genética , Óvulo Vegetal/crecimiento & desarrollo , Plantas Modificadas Genéticamente , Polen/genética , Polen/crecimiento & desarrollo , Unión Proteica , Proteína Fosfatasa 2/genéticaRESUMEN
Potassium channels are important for many physiological functions in plants, one of which is to regulate plant adaptation to stress conditions. In this study, a K(+) channel PutAKT1 cDNA was isolated from the salt-tolerant plant Puccinellia tenuiflora. A phylogenetic analysis showed that PutAKT1 belongs to the AKT1-subfamily in the Shaker K(+) channel family. PutAKT1 was localized in the plasma membrane and it was preferentially expressed in the roots. The expression of PutAKT1 was induced by K(+)-starvation stress in the roots and was not down-regulated by the presence of excess Na(+). Arabidopsis plants over-expressing PutAKT1 showed enhanced salt tolerance compared to wild-type plants as shown by their shoot phenotype and dry weight. Expression of PutAKT1 increased the K(+) content of Arabidopsis under normal, K(+)-starvation, and NaCl-stress conditions. Arabidopsis expressing PutAKT1 also showed a decrease in Na(+) accumulation both in the shoot and in the root. These results suggest that PutAKT1 is involved in mediating K(+) uptake (i) both in low- and in high-affinity K(+) uptake range, and (ii) unlike its homologs in rice, even under salt-stress condition.
Asunto(s)
Arabidopsis/metabolismo , Proteínas de Plantas/metabolismo , Poaceae/genética , Canales de Potasio/metabolismo , Potasio/metabolismo , Secuencia de Aminoácidos , Arabidopsis/genética , Clonación Molecular , ADN Complementario/genética , Regulación de la Expresión Génica de las Plantas , Datos de Secuencia Molecular , Proteínas de Plantas/genética , Raíces de Plantas/metabolismo , Brotes de la Planta/metabolismo , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/metabolismo , Poaceae/metabolismo , Canales de Potasio/genética , ARN de Planta/genética , Plantas Tolerantes a la Sal/genética , Plantas Tolerantes a la Sal/metabolismo , Sodio/metabolismo , Cloruro de Sodio/farmacología , Estrés FisiológicoRESUMEN
Isu is a scaffold protein involved in mitochondrial iron-sulfur-cluster biogenesis, which affects redox and iron homeostasis in human and yeast cells. A BLASTP search identified two putative Isu genes in rice, and we designated one of them as OsIsu1. When expressed in onion epidermal cells, OsIsu1::GFP was localized to the mitochondria. Northern analysis showed that OsIsu1 was down-regulated in iron-deficient rice root. OsIsu1 promoter-GUS was introduced into Arabidopsis thaliana and histochemical GUS-staining showed that OsIsu1 expression was regulated in a stage- and tissue-specific manner. OsIsu1 was expressed ectopically in Arabidopsis under the control of the CaMV35S promoter, which increased weight of plants.
Asunto(s)
Regulación de la Expresión Génica , Proteínas Hierro-Azufre/biosíntesis , Proteínas Mitocondriales/biosíntesis , Oryza/fisiología , Arabidopsis/química , Arabidopsis/genética , Fusión Artificial Génica , Northern Blotting , Células Cultivadas , Genes Reporteros , Glucuronidasa/genética , Glucuronidasa/metabolismo , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Proteínas Hierro-Azufre/genética , Proteínas Mitocondriales/genética , Cebollas , Oryza/química , Raíces de Plantas/química , Plantas Modificadas Genéticamente/química , Plantas Modificadas Genéticamente/genéticaRESUMEN
To understand the mechanisms of ion homeostasis in salt-tolerant and salt-sensitive plants, cDNAs for a high-affinity K(+) transporter PhaHKT1 were isolated from salt-sensitive (Utsunomiya) and salt-tolerant (Nanpi, Enchi) reed plants. A cDNA of Utsunomiya (PhaHKT1-u) contained two insertions in the region corresponding to the first and second introns of the PhaHKT1 gene, which resulted in a sequence 141 amino acid residues shorter than that of Nanpi. Expression of PhaHKT1 mRNA was detected in the roots of Nanpi and Enchi plants under K(+) starvation conditions and also under Na(+) treatment conditions, whereas it was only slightly detected in the roots of Utsunomiya plants under each of these conditions. In the upper parts, PhaHKT1 expression was detected in the Utsunomiya plants, and two signals were obtained in the Nanpi and Enchi plants under all and K(+) starvation conditions, respectively. Yeasts expressing the PhaHKT1 of Nanpi (PhaHKT1-n) or the PhaHKT1 of Enchi (PhaHKT1-e) grew better in the presence of NaCl than yeast expressing PhaHKT1-u. Furthermore, yeast expressing a chimeric cDNA containing the 5' region of the Utsunomiya gene and the 3' region of the Nanpi gene had partial salt tolerance, and yeast expressing a chimeric cDNA containing the 5' region of the Nanpi gene and the 3' region of the Utsunomiya gene had a reduced ability to take up ions. These results suggest that PhaHKT1 plays an important role in the acquisition of K(+) and maintenance of ion balance under saline conditions.
Asunto(s)
Proteínas de Transporte de Catión/metabolismo , Proteínas de Plantas/metabolismo , Poaceae/metabolismo , Potasio/metabolismo , Cloruro de Sodio/metabolismo , Simportadores/metabolismo , Secuencia de Aminoácidos , Proteínas de Transporte de Catión/genética , Clonación Molecular , ADN Complementario , Expresión Génica , Datos de Secuencia Molecular , Proteínas de Plantas/genética , Poaceae/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Simportadores/genética , Transformación GenéticaRESUMEN
VB12-independent methionine synthase is present in higher plants, and catalyzes the methylation of C-homocysteine to form methionine, which is very important for methylation reactions and syntheses of polyamines and ethylene. Under the alkaline condition, using cDNA-RAPD method, a new VB12-independent methionine synthase gene has been cloned and characterized for the first time in rice in this study. The results exhibited that, the cDNA gene entailed 2740 bp, had single copy in the rice genome and encoded peptide of 765 amino acids, the peptide showed 92% and 83% identity with that from Mesembryanthemum cystallinum (U84889) and Cathararanthus roseus (X83499), respectively. It enhanced the transcription more greatly after sodium carbonate treatment for 12 h and 24 h than that of sodium chloride treatment, and then obviously reduced in 48 h later, suggesting that it is related to this stress tolerance in rice.