RESUMEN
Enriching zinc (Zn) and selenium (Se) levels, while reducing cadmium (Cd) concentration in rice grains is of great benefit for human diet and health. Large natural variations in grain Zn, Se, and Cd concentrations in different rice accessions enable Zn/Se-biofortification and Cd-minimization through molecular breeding. Here, we report the development of new elite varieties by pyramiding major quantitative trait loci (QTLs) that significantly contribute to high Zn/Se and low Cd accumulation in grains. A chromosome segment substitution line CSSLGCC7 with the PA64s-derived GCC7 allele in the 93-11 background, exhibited steadily higher Mn and lower Cd concentrations in grains than those of 93-11. This elite chromosome segment substitution line (CSSL) was used as the core breeding material to cross with CSSLs harboring other major QTLs for essential mineral elements, especially CSSLGZC6 for grain Zn concentration and CSSLGSC5 for grain Se concentration. The CSSLGCC7+GZC6 and CSSLGCC7+GSC5 exhibited lower Cd concentration with higher Zn and Se concentrations in grains, respectively. Our study thus provides elite materials for rice breeding targeting high Zn/Se and low Cd concentrations in grains.
Asunto(s)
Cadmio/metabolismo , Oryza/metabolismo , Selenio/metabolismo , Zinc/metabolismo , Alelos , Grano Comestible/genética , Grano Comestible/metabolismo , Oryza/genética , Sitios de Carácter Cuantitativo/genéticaRESUMEN
To better understand the molecular mechanisms behind plant growth and leaf senescence in monocot plants, we identified a mutant exhibiting dwarfism and an early-senescence leaf phenotype, termed dwarf and early-senescence leaf1 (del1). Histological analysis showed that the abnormal growth was caused by a reduction in cell number. Further investigation revealed that the decline in cell number in del1 was affected by the cell cycle. Physiological analysis, transmission electron microscopy, and TUNEL assays showed that leaf senescence was triggered by the accumulation of reactive oxygen species. The DEL1 gene was cloned using a map-based approach. It was shown to encode a pectate lyase (PEL) precursor that contains a PelC domain. DEL1 contains all the conserved residues of PEL and has strong similarity with plant PelC. DEL1 is expressed in all tissues but predominantly in elongating tissues. Functional analysis revealed that mutation of DEL1 decreased the total PEL enzymatic activity, increased the degree of methylesterified homogalacturonan, and altered the cell wall composition and structure. In addition, transcriptome assay revealed that a set of cell wall function- and senescence-related gene expression was altered in del1 plants. Our research indicates that DEL1 is involved in both the maintenance of normal cell division and the induction of leaf senescence. These findings reveal a new molecular mechanism for plant growth and leaf senescence mediated by PECTATE LYASE-LIKE genes.
Asunto(s)
Genes de Plantas , Oryza/enzimología , Oryza/genética , Desarrollo de la Planta/genética , Hojas de la Planta/crecimiento & desarrollo , Polisacárido Liasas/genética , Secuencia de Aminoácidos , Recuento de Células , Ciclo Celular/genética , Muerte Celular/genética , Pared Celular/metabolismo , Clonación Molecular , Esterificación , Perfilación de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Modelos Biológicos , Mutación/genética , Oryza/crecimiento & desarrollo , Pectinas/metabolismo , Fenotipo , Filogenia , Hojas de la Planta/genética , Hojas de la Planta/ultraestructura , Polisacárido Liasas/química , Polisacárido Liasas/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Transcriptoma/genéticaRESUMEN
DEAD-box proteins comprise a large protein family. These proteins function in all types of processes in RNA metabolism and are highly conserved among eukaryotes. However, the precise functions of DEAD-box proteins in rice physiology and development remain unclear. In this study, we identified a rice DEAD-box protein, OsRH17, that contains a DEAD domain and all of the common conserved motifs of DEAD-box RNA helicases. OsRH17 was specifically expressed in pollen and differentiated callus and upregulated by application of the plant hormones naphthyl acetic acid (NAA) and abscisic acid (ABA). The OsRH17:GFP fusion protein was localized to the nucleus. Tiny amounts of OsRH17 and partial fragments (N-427 and C-167) were detected when they were expressed in Escherichia coli, a prokaryote. Growth of the host cells was suppressed in E. coli by OsRH17, N-427 or C-167, and this suppression was independent of the concentration of the NaCl in the medium. Expression analysis of rRNAs in E. coli revealed that the 16S rRNA precursor accumulated in transgenic E. coli cells, and the relative growth rate was inversely proportional to the levels of pre-16S rRNA accumulation. Results suggested that OsRH17 may play a role in ribosomal biogenesis and suppress 16S rRNA maturation in E. coli. No visible phenotype was observed in transgenic yeast and rice (overexpressing OsRH17, N-427, and C-167, as well as OsRH17 knockdown), and even in some abiotic and biotic stresses, which could be due to the redundancy in rice under normal conditions.
Asunto(s)
ARN Helicasas DEAD-box/genética , Escherichia coli/genética , Regulación de la Expresión Génica de las Plantas , Oryza/genética , Proteínas de Plantas/metabolismo , ARN Ribosómico 16S/genética , Prueba de Complementación Genética , Oryza/enzimología , Fenotipo , Filogenia , Reguladores del Crecimiento de las Plantas/metabolismo , Proteínas de Plantas/genética , Polen/metabolismo , Cloruro de Sodio/químicaRESUMEN
Optimizing the beneficial mineral elements in rice grains is of interest for rice breeders. To study the environmental effects on mineral accumulation in rice grains, we grew a double-haploid (DH) population derived from the cross between cultivars Chunjiang 06 (CJ06, a japonica rice) and TN1 (an indica rice) under two different ecological environments (Lingshui and Hangzhou, China) and determined the content of Ca, Fe, K, Mg, Mn, P, and Zn in brown rice. These contents show transgressive variation among the DH lines. Subsequently, the quantitative trait loci (QTLs) for mineral accumulation in rice grain were mapped on the chromosomes using CJ06/TN1 population. For the 7 mineral elements investigated, 23 and 9 QTLs were identified for Lingshui and Hangzhou, respectively. Of these, 24 QTLs were reported for the first time in this study and 8 QTLs are consistent with previous reports. Only 2 QTLs for Mg accumulation have been detected in both environments, indicating that mineral accumulation QTLs in rice grains are largely environment dependent. Additionally, co-localizations of QTLs for Mn and Zn, Mg and P, and Mg and Mn accumulation have been observed, implying that these loci might be involved in the accumulation of different elements. Furthermore, the QTLs for the accumulation of Fe, K, Mg, Mn, P, and Zn were mapped to a region close to each other on chromosomes 8 and 9, suggesting that clusters of genes exist on chromosomes 8 and 9. Further characterization of these QTLs will provide a better understanding of the molecular mechanism responsible for mineral accumulation in rice grains.