RESUMEN
Plant R2R3-MYB transcription factors are encoded by more than 100 copies of genes. In this study, we attempted to isolate some members of the R2R3-MYB superfamily involved in regulation of nitrogen fixation in legumes. A library of 300 recombinant plasmid clones containing the R2R3-MYB fragments of the superfamily was screened by differential hybridization to isolate R2R3-MYB genes whose expression was up-regulated under nitrogen nutrient-limited conditions. Two groups of clones were identified, each of which seemed to represent a gene responsive to nitrogen starvation. The entire coding regions for the genes were further isolated by PCR and were designated LjMYB101 and LjMYB102. By screening a genomic library of Lotus japonicus with a probe derived from LjMYB101, the third gene, LjMYB103, was isolated. In addition, a candidate for the soybean orthologue of LjMYB101 was isolated and designated GmMYB101. Sequence alignment of the genes with members of the plant R2R3-MYB superfamily showed that they all belonged to the subgroup 10 of the superfamily. The expression analysis of the genes showed that the organ-specific and nitrate-regulated expression profile of MYB101 was very similar to that of CHS in Lotus as well as in soybean, suggesting a possible role for MYB101 in regulation of flavonoid biosynthesis in response to nitrate starvation. On the other hand, an interesting relationship, in structure and function, was found between LjMYB101 and LjGln1, suggesting an alternative role for MYB101 in regulation of nitrogen metabolism.
Asunto(s)
Glycine max/genética , Lotus/genética , Familia de Multigenes/genética , Nitrógeno/farmacología , Proteínas de Plantas/genética , Proteínas Proto-Oncogénicas c-myb/genética , Factores de Transcripción/genética , Secuencia de Aminoácidos , Secuencia de Bases , Southern Blotting , Clonación Molecular , ADN Complementario/química , ADN Complementario/genética , ADN Complementario/aislamiento & purificación , ADN de Plantas/química , ADN de Plantas/genética , ADN de Plantas/aislamiento & purificación , Dosificación de Gen , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Lotus/efectos de los fármacos , Lotus/crecimiento & desarrollo , Datos de Secuencia Molecular , Nitratos/farmacología , Filogenia , Regiones Promotoras Genéticas/genética , Alineación de Secuencia , Análisis de Secuencia de ADN , Homología de Secuencia de Aminoácido , Homología de Secuencia de Ácido Nucleico , Proteínas de Soja/genética , Glycine max/efectos de los fármacos , Glycine max/crecimiento & desarrollo , Regulación hacia ArribaRESUMEN
Seed coat color in soybeans is determined by the I (Inhibitor) locus. The dominant I allele inhibits seed coat pigmentation, and it has been suggested that there is a correlation between the inhibition of pigmentation by the I allele and chalcone synthase (CHS) gene silencing in the seed coat. Analysis of spontaneous mutations from I to i has shown that these mutations are closely related to the deletion of one of the CHS genes (designated ICHS1). In soybeans with the I/I genotype (cv. Miyagi shirome), a truncated form of the CHS gene (CHS3) is located in an inverse orientation 680 bp upstream of ICHS1, and it was previously suggested that the truncated CHS3- ICHS1 cluster might be involved in CHS gene silencing in the seed coat. In the current study, the truncated CHS3- ICHS1 cluster was compared with the corresponding region of pigmented seed coat mutants in which I had changed to i in Miyagi shirome and in the strain Karikei 584. In the Karikei 584 mutant, the truncated CHS3-ICHS1 cluster was retained and the sequence diverged at a point immediately upstream (32 bp) of this cluster. The sequences upstream of the points of divergence in both mutants almost perfectly matched a part of the registered sequence in a soybean BAC clone containing the soybean cyst nematode resistance-associated gene, and inspection of the sequences suggested that the sequence divergence of the CHS gene in the Karikei 584 and Miyagi shirome mutants was due to an unequal crossing-over via 4-bp or 5-bp short repeats, respectively.