RESUMEN
OsINV2, a rice vacuolar invertase isoform, was assessed for its functional roles in plant growth and development with key focus on its agronomic traits such as grain weight, grain filling percentage, grain number and dry weights at various stages until harvest. Lack of differences between the wild-type and the mutants with respect to any of the aforementioned traits tested revealed a possibility of functional compensation of OsINV2 in the mutants conceivably by its isoform. This was confirmed by OsINV2 promoter::GUS studies, where its spatial and temporal expression in the panicle elongation stages showed that although OsINV2 expression was observed from the stage with young panicles ~1 cm in length to the flag leaf stage, significant differences with respect to panicle and spikelet phenotypes between the wild-type and the mutant were not present. However, complement lines displaying an overexpression phenotype of OsINV2 possessed a higher stem non-structural carbohydrate content under both monoculm and normal tillering conditions. A trade-off between the spikelet number and grain weight in the complement lines grown under monoculm conditions was also observed, pointing towards the necessity of OsINV2 regulation for grain yield-related traits.
Asunto(s)
Oryza , Grano Comestible , Fenotipo , Isoformas de Proteínas , beta-FructofuranosidasaRESUMEN
BACKGROUND: Rice is a major crop feeding the majority of the global population, and increasing its sink strength is one of the modes to alleviate the declining availability of food for the rapidly growing world population. We demonstrate a role for an important rice vacuolar invertase isoform, OsINV3, in sink strength determination. RESULTS: OsINV3 mutants showed shorter panicles with lighter and smaller grains, owing to a smaller cell size on the outer and inner surfaces of the palea and lemma as observed by scanning electron microscopy. Further, strong promoter::GUS expression was observed in the palea, lemma and the rachis branches in the young elongating panicles, which supported the role of OsINV3 in cell expansion and thus, in spikelet size and panicle length determination. Size of the spikelet was found to directly influence the grain weight, which was confirmed by the lack of differences in weights of hulled grain for differently segregated alleles in the heterozygous lines. Assessment of field grown mutants not only revealed a drastic reduction in the percentage of ripened grain, 1000-grain weight and final yield, but also significantly reduced partitioning of assimilates to the panicles, whereby the total dry weight remained unaffected. Determination of the non-structural carbohydrate contents revealed a lower hexose-to-sucrose ratio in the panicles of the mutants from panicle initiation to 10 days after heading, a stage that identifies as the critical pre-storage phase of grain filling, whereas the starch contents were not affected. In addition, strong promoter::GUS expression was observed in the dorsal end of ovary during the pre-storage phase until 6 days after flowering, highlighting a function for OsINV3 in monitoring the initial grain filling stage. CONCLUSIONS: OsINV3 was found to regulate spikelet size by playing a key role in cell expansion, driving the movement of assimilates for grain filling by modulating the hexose-to-sucrose ratio, contributing in grain weight determination and thus, the grain yield.
RESUMEN
Viscosity, a crucial characteristic for rice palatability, is affected by endosperm characters. We compared correlations between differences in viscosity of japonica rice with various palatability and endosperm characters. Changes in apparent amylose and protein contents (AAC% and PC%, respectively) and amylopectin side-chain distribution and the relationship of these traits with palatability were investigated in superior and inferior spikelets of good cultivars with low amylose content from Hokkaido and common cultivars from northeastern Japan, using rapid visco analyzer characteristics and rice-grain microstructures. Significant differences occurred in PC%, AAC%, breakdown, setback, peak time, and pasting temperature of different cultivars and grain positions. Amylopectin components showed remarkable differences in grain surfaces, surface layers, and section structure between the grain varieties. Hokkaido cultivars showed better viscosity than northeastern cultivars, particularly initial stage grains. Correlation analysis indicated viscosity was mainly AAC%-dependent, whereas differences in endosperm characteristics between spikelet positions were mainly due to grain-filling temperature.
Asunto(s)
Amilosa/química , Oryza/química , Japón , Oryza/clasificación , Polvos/análisis , Semillas/química , Temperatura , ViscosidadRESUMEN
Sucrose phosphate synthase (SPS) has been shown to mediate sucrose/starch ratio in plant leaves through studies of 'starch leaf' species that mainly accumulate starch in their leaves. However, the contribution of SPS to sucrose/starch ratio in rice leaves, which mainly accumulate sucrose (i.e., 'sugar leaf'), has not been confirmed due to inconsistencies in the results of previous studies. In this study, we analyzed mutant lines with reduced SPS activity, which were generated using Tos17 insertion, RNAi, and the CRISPR/Cas9 system. The knockdown and knockout mutants of OsSPS1 showed a 29-46% reduction in SPS activity in the leaves, but the carbohydrate content in the leaves and plant growth were not significantly different from those of wild-type plants. In a double knockout mutant of OsSPS1 and OsSPS11 (sps1/sps11), an 84% reduction in leaf SPS activity resulted in higher starch accumulation in the leaves than in the wild-type leaves. However, the sps1/sps11 plants grew normally, which is in contrast to the inhibited growth of SPS mutants of Arabidopsis thaliana, a typical starch leaf plant. These results suggest that SPS has a smaller effect on the sucrose/starch ratio in leaves and growth of rice than on starch leaf species.
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Metabolismo de los Hidratos de Carbono , Glucosiltransferasas/metabolismo , Oryza/enzimología , Desarrollo de la Planta , Secuencia de Bases , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , Datos de Secuencia Molecular , Oryza/genética , Oryza/crecimiento & desarrollo , Interferencia de ARNRESUMEN
In rice (Oryza sativa L.), chilling-induced male sterility increased when plants experienced low water temperature (Tw , 18 °C for 14 d) before panicle initiation. The number of mature pollen grains after chilling at the booting stage (12 °C for 5 d) was only 45% of total pollen grains in low-Tw plants, whereas it was 71% in normal-Tw plants (Tw not controlled; approximately 23 °C under air temperature of 26 °C/21 °C, day/night). Microarray and quantitative PCR analyses showed that many stress-responsive genes (including OsFKBP65 and genes encoding the large heat shock protein OsHSP90.1, heat-stress transcription factors and many small heat shock proteins) were strongly up-regulated by chilling in normal-Tw spikelets, but were unaffected or even down-regulated by chilling in low-Tw spikelets. OsAPX2 and genes encoding some other antioxidant enzymes were also significantly down-regulated by low Tw in chilled spikelets. The levels of lipid peroxidation products (malondialdehyde equivalents) were significantly increased in low-Tw spikelets by chilling. Ascorbate peroxidase activity in chilled spikelets was significantly lower in low-Tw plants than in normal-Tw plants. Our data suggest that an OsFKBP65-related chilling response, which protects proteins from oxidative damage, is indispensable for chilling tolerance but is lost in low-Tw spikelets.
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Proteínas de Unión al ADN/genética , Regulación de la Expresión Génica de las Plantas , Proteínas de Choque Térmico/genética , Oryza/fisiología , Proteínas de Plantas/genética , Factores de Transcripción/genética , Ácido Abscísico/metabolismo , Frío , Proteínas de Unión al ADN/metabolismo , Perfilación de la Expresión Génica , Factores de Transcripción del Choque Térmico , Proteínas de Choque Térmico/metabolismo , Peroxidación de Lípido , Malondialdehído/metabolismo , Análisis de Secuencia por Matrices de Oligonucleótidos , Oryza/genética , Estrés Oxidativo , Reguladores del Crecimiento de las Plantas/metabolismo , Infertilidad Vegetal/genética , Proteínas de Plantas/metabolismo , Polen/genética , Polen/fisiología , Estrés Fisiológico , Factores de Transcripción/metabolismo , Agua/fisiologíaRESUMEN
The molecular function of an isoform of sucrose phosphate synthase (SPS) in rice, OsSPS1, was investigated using gene-disruption mutant lines generated by retrotransposon insertion. The progeny of the heterozygote of disrupted OsSPS1 (SPS1(+/-)) segregated into SPS1(+/+), SPS1(+/-), and SPS1(-/-) at a ratio of 1:1:0. This distorted segregation ratio, together with the expression of OsSPS1 in the developing pollen revealed by quantitative RT-PCR analysis and promoter-beta-glucuronidase (GUS) fusion assay, suggested that the disruption of OsSPS1 results in sterile pollen. This hypothesis was reinforced by reciprocal crosses of SPS1(+/-) plants with wild-type plants in which the disrupted OsSPS1 was not paternally transmitted to the progeny. While the pollen grains of SPS(+/-) plants normally accumulated starch during their development, pollen germination on the artificial media was reduced to half of that observed in the wild-type control. Overall, our data suggests that sucrose synthesis via OsSPS1 is essential in pollen germination in rice.
Asunto(s)
Genes de Plantas , Glucosiltransferasas/genética , Mutación , Oryza/genética , Proteínas de Plantas/genética , Polen/metabolismo , Sacarosa/metabolismo , Cruzamientos Genéticos , Glucosiltransferasas/metabolismo , Heterocigoto , Oryza/enzimología , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Retroelementos , Almidón/metabolismoRESUMEN
BACKGROUND: To identify genes that potentially regulate the accumulation, mobilization, and transport of photoassimilates in rice (Oryza sativa L.) leaves, we recently screened a mutant collection of rice by iodine staining to visualize leaf starch contents. From this screening, we isolated a rice mutant that exhibits hyperaccumulation of starch in leaves and designated it as the Leaf Starch Excess 1 (LSE1) mutant. Here, we report two other rice LSE mutants, LSE2 and LSE3. RESULTS: Unlike lse1 plants, lse2 and lse3 plants displayed retarded growth; lse2 showed an extremely dwarf phenotype and rarely survived in paddy fields; lse3 showed inhibited growth with pale green leaf blades, low tiller numbers, reduced height, and low grain yield. In lse2 and lse3 plants, the mature source leaves contained larger amounts of starch and sucrose than those in wild-type and lse1 plants. Furthermore, microscopic observations of leaf transverse sections indicated that hyperaccumulation of starch in chloroplasts of mesophyll and bundle sheath cells occurred in lse2 and lse3 plants, while that in vascular cells was noticeable only in lse3 leaves. CONCLUSIONS: The distinct phenotypes of these three LSE mutants suggest that the LSE2 and LSE3 mutations occur because of disruption of novel genes that might be involved in the path of sucrose transport from mesophyll cells to phloem sieve elements in rice leaves, the mechanism for which has not yet been elucidated.
RESUMEN
In rice (Oryza sativa L.), tiller angle - defined as the angle between the main culm and its side tillers - is one of the important factors involved in light use efficiency. To clarify the relationship between tiller angle, gravitropism and stem-starch accumulation, we investigated the shoot gravitropic response of a low stem-starch rice mutant which lacks a large subunit of ADP-glucose pyrophosphorylase (AGP), called OsAGPL1 and exhibits relatively spread tiller angle. The insensitive gravitropic response exhibited by the mutant led us to the conclusion that insensitivity of gravitropism caused by stem-starch reduction splayed the tiller angle. Furthermore, since another AGP gene called OsAGPL3 was expressed at considerable levels in graviresponding sites, we generated a double mutant lacking both OsAGPL1 and OsAGPL3. The double mutant exhibited still lower stem-starch content, less sensitive gravitropic response and greater tiller angle spread than the single mutants. This indicated that the expansion of the tiller angle caused by the reduction in starch level was intense according to the extent of the reduction. We found there were no significant differences between the double mutant and wild-type plants in terms of dry matter production. These results provided new insight into the importance of stem-starch accumulation and ideal plant architecture.
RESUMEN
To identify potential regulators of photoassimilate partitioning, we screened for rice mutant plants that accumulate high levels of starch in the leaf blades, and a mutant line leaf starch excess 1 (LSE1) was obtained and characterized. The starch content in the leaf blades of LSE1 was more than 10-fold higher than that in wild-type plants throughout the day, while the sucrose content was unaffected. The gene responsible for the LSE1 phenotype was identified by gene mapping to be a gene encoding α-glucan water dikinase, OsGWD1 (Os06g0498400), and a 3.4-kb deletion of the gene was found in the mutant plant. Despite the hyperaccumulation of starch in their leaf blades, LSE1 plants exhibited no significant change in vegetative growth, presenting a clear contrast to the reported mutants of Arabidopsis thaliana and Lotus japonicus in which disruption of the genes for α-glucan water dikinase leads to marked inhibition of vegetative growth. In reproductive growth, however, LSE1 exhibited fewer panicles per plant, lower percentage of ripened grains and smaller grains; consequently, the grain yield was lower in LSE1 plants than in wild-type plants by 20~40%. Collectively, although α-glucan water dikinase was suggested to have universal importance in leaf starch degradation in higher plants, the physiological priority of leaf starch in photoassimilate allocation may vary among plant species.
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Although sucrose plays a role in sugar sensing and its signaling pathway, little is known about the regulatory mechanisms of the expressions of plant sucrose-related genes. Our previous study on the expression of the sucrose phosphate synthase gene family in rice (OsSPSs) suggested the involvement of sucrose sensing and/or circadian rhythm in the transcriptional regulation of OsSPS. To examine whether the promoters of OsSPSs can be controlled by sugars and circadian clock, we produced transgenic rice plants harboring a promoter-luciferase construct for OsSPS1 or OsSPS11 and analyzed the changes in the promoter activities by monitoring bioluminescence from intact transgenic plants in real-time. Transgenic plants fed sucrose, glucose, or mannitol under continuous light conditions showed no changes in bioluminescence intensity; meanwhile, the addition of sucrose increased the concentration of sucrose in the plants, and the mRNA levels of OsSPS remained constant. These results suggest that these OsSPS promoters may not be regulated by sucrose levels in the tissues. Next, we investigated the changes in the promoter activities under 12-h light/12-h dark cycles and continuous light conditions. Under the light-dark cycle, both OsSPS1 and OsSPS11 promoter activities were low in the dark and increased rapidly after the beginning of the light period. When the transgenic rice plants were moved to the continuous light condition, both P OsSPS1 ::LUC and P OsSPS11 ::LUC reporter plants exhibited circadian bioluminescence rhythms; bioluminescence peaked during the subjective day with a 27-h period: in the early morning as for OsSPS1 promoter and midday for OsSPS11 promoter. These results indicate that these OsSPS promoters are controlled by both light illumination and circadian clock and that the regulatory mechanism of promoter activity differs between the two OsSPS genes.
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Starch accumulated in rice (Oryza sativa L.) stems before heading as nonstructural carbohydrates (NSCs) is reported to be important for improving and stabilising grain yield. To evaluate the importance of stem starch, we investigated a retrotransposon (Tos17) insertion rice mutant lacking a gene encoding a large subunit of ADP-glucose pyrophosphorylase (AGP) called OsAGPL1 or OsAPL3. The AGP activity and starch contents of the mutant were drastically reduced in the stem (i.e. leaf sheath and culm) but not in the leaf blade or endosperm. This starch reduction in the leaf sheaths of the mutant was complemented by the introduction of wild-type OsAGPL1. These results strongly suggest that OsAGPL1 plays a principal role in stem starch accumulation. Field experimentations spanning 2 years revealed that the mutant plants were shorter than the wild-type plants. Moreover, the tiller number and angle were larger in the mutant plants than the wild-type plants, but the dry weight at heading stage was not different. The grain yield was slightly lower in control plots without shading treatment. However, this difference increased substantially with shading. Therefore, stem starch is indispensable for normal ripening under low irradiance conditions and probably contributes to the maintenance of appropriate plant architecture.
RESUMEN
Calcium-dependent protein kinases (CDPKs) constitute a large multigene family in various plant species. CDPKs have been shown to have important roles in various physiological processes, including plant growth and development and abiotic and biotic stress responses in plants. Functional analysis using gain-of-function and loss-of-function mutants has revealed the biological function of CDPKs in planta. Several CDPKs have been shown to be essential factors in abiotic stress tolerance, positively or negatively regulating stress tolerance by modulating ABA signaling and reducing the accumulation of reactive oxygen species (ROS). This review summarizes recent results describing the biological function of CDPKs that are involved in abiotic stress tolerance.
Asunto(s)
Plantas/enzimología , Proteínas Quinasas/metabolismo , Transducción de Señal , Estrés Fisiológico , Ácido Abscísico/metabolismo , Proteínas Quinasas/química , Especies Reactivas de Oxígeno/metabolismoRESUMEN
Calcium-dependent protein kinases (CDPKs) regulate the downstream components in calcium signaling pathways. We investigated the effects of overexpression and disruption of an Oryza sativa (rice) CDPK (OsCPK12) on the plant's response to abiotic and biotic stresses. OsCPK12-overexpressing (OsCPK12-OX) plants exhibited increased tolerance to salt stress. The accumulation of hydrogen peroxide (H(2) O(2) ) in the leaves was less in OsCPK12-OX plants than in wild-type (WT) plants. Genes encoding reactive oxygen species (ROS) scavenging enzymes (OsAPx2 and OsAPx8) were more highly expressed in OsCPK12-OX plants than in WT plants, whereas the expression of the NADPH oxidase gene, OsrbohI, was decreased in OsCPK12-OX plants compared with WT plants. Conversely, a retrotransposon (Tos17) insertion mutant, oscpk12, and plants transformed with an OsCPK12 RNA interference (RNAi) construct were more sensitive to high salinity than were WT plants. The level of H(2) O(2) accumulation was greater in oscpk12 and OsCPK12 RNAi plants than in the WT. These results suggest that OsCPK12 promotes tolerance to salt stress by reducing the accumulation of ROS. We also observed that OsCPK12-OX seedlings had increased sensitivity to abscisic acid (ABA) and increased susceptibility to blast fungus, probably resulting from the repression of ROS production and/or the involvement of OsCPK12 in the ABA signaling pathway. Collectively, our results suggest that OsCPK12 functions in multiple signaling pathways, positively regulating salt tolerance and negatively modulating blast resistance.
Asunto(s)
Proteínas Quinasas Dependientes de Calcio-Calmodulina/metabolismo , Magnaporthe/patogenicidad , Oryza/microbiología , Oryza/fisiología , Proteínas de Plantas/metabolismo , Ácido Abscísico/metabolismo , Ácido Abscísico/farmacología , Ascorbato Peroxidasas/genética , Proteínas Quinasas Dependientes de Calcio-Calmodulina/genética , Resistencia a la Enfermedad , Regulación Enzimológica de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Peróxido de Hidrógeno/metabolismo , Mutación , NADPH Oxidasas/genética , Oryza/efectos de los fármacos , Enfermedades de las Plantas/microbiología , Hojas de la Planta/metabolismo , Hojas de la Planta/microbiología , Proteínas de Plantas/genética , Plantas Modificadas Genéticamente , Interferencia de ARN , Especies Reactivas de Oxígeno/metabolismo , Tolerancia a la SalRESUMEN
The rice genome contains 5 isogenes for sucrose phosphate synthase (SPS), the key enzyme in sucrose synthesis; however, little is known about their transcriptional regulation. In order to determine the expression patterns of the SPS gene family in rice plants, we conducted an expression analysis in various tissues and developmental stages by real-time quantitative RT-PCR. At the transcript level, the rice SPS genes, particularly SPS1, were preferentially expressed in source tissues, whereas SPS2, SPS6, and SPS8 were expressed equally in source and sink tissues. We also investigated diurnal changes in SPS gene expression, SPS activity, and soluble sugar content in leaf blades. Interestingly, the expression of all the SPS genes, particularly that of SPS1 and SPS11, tended to be higher at night when the activation state of the SPS proteins was low, and the mRNA levels of SPS1 and SPS6 were negatively correlated with sucrose content. Furthermore, the temporal patterns of SPS gene expression and sugar content under continuous light conditions suggested the involvement of endogenous rhythm and/or sucrose sensing in the transcriptional regulation of SPS genes. Our data revealed differential expression patterns in the rice SPS gene family and part of the complex mechanisms of their transcriptional control.
Asunto(s)
Ritmo Circadiano/genética , Regulación Enzimológica de la Expresión Génica/genética , Glucosiltransferasas/genética , Oryza/fisiología , Carbohidratos/análisis , Regulación del Desarrollo de la Expresión Génica/genética , Regulación de la Expresión Génica de las Plantas/genética , Germinación , Glucosiltransferasas/metabolismo , Luz , Familia de Multigenes/genética , Especificidad de Órganos/genética , Oryza/enzimología , Oryza/genética , Filogenia , Hojas de la Planta/enzimología , Hojas de la Planta/genética , Hojas de la Planta/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , ARN Mensajero/genética , Plantones/enzimología , Plantones/genética , Plantones/fisiologíaRESUMEN
The excessive application of nitrogen fertilizer to maximize crop yields causes negative environmental effects such as pollution and ecological imbalance. To overcome this problem, researchers have attempted to improve the nitrogen assimilation capacity of crops. Maize Dof1 (ZmDof1) is a plant-specific transcription factor shown to promote nitrogen assimilation in Arabidopsis thaliana (Arabidopsis) even under nitrogen-deficient conditions. The present study examines the effect of the introduction of the ZmDof1 gene on carbon and nitrogen assimilation in rice. ZmDof1 induced the expression of phosphoenolpyruvate carboxylase (PEPC) genes in transgenic rice plants and transactivated the PEPC promoters in protoplast transient assays, showing similar effects in rice as in Arabidopsis. Transgenic rice expressing ZmDof1 and grown in the presence of 360 µm (nitrogen-sufficient) or 90 µm (nitrogen-deficient) of nitrogen concentrations showed modulation of metabolite content and gene expression associated with the anaplerotic pathway for the TCA cycle, suggesting an increased carbon flow towards nitrogen assimilation. Furthermore, increases in carbon and nitrogen amounts per seedling were found in Dof1 rice grown under nitrogen-deficient conditions. Nitrogen deficiency also resulted in the predominant distribution of nitrogen to roots, accompanied by significant increases in root biomass and modification of the shoot-to-root ratio. Measurement of the CO2 gas exchange rate showed a significant increase in the net photosynthesis rate in Dof1 rice under nitrogen-deficient conditions. Taken these together, the present study displayed that ZmDof1 expression in rice could induce gene expressions such as PEPC genes, modulate carbon and nitrogen metabolites, increase nitrogen assimilation and enhance growth under low-nitrogen conditions.
Asunto(s)
Carbono/metabolismo , Genes de Plantas , Nitrógeno/metabolismo , Oryza/metabolismo , Fosfoenolpiruvato Carboxilasa/metabolismo , Factores de Transcripción/genética , Aminoácidos/análisis , Aminoácidos/metabolismo , Southern Blotting , Dióxido de Carbono/metabolismo , Ciclo del Ácido Cítrico , Regulación de la Expresión Génica de las Plantas , Vectores Genéticos/genética , Vectores Genéticos/metabolismo , Oryza/genética , Oryza/crecimiento & desarrollo , Fotosíntesis , Hojas de la Planta/metabolismo , Raíces de Plantas/metabolismo , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/crecimiento & desarrollo , Plantas Modificadas Genéticamente/metabolismo , Protoplastos/metabolismo , Factores de Transcripción/metabolismo , Zea mays/genéticaRESUMEN
Calcium acts as a messenger in various signal transduction pathways in plants. Calcium-dependent protein kinases (CDPKs) play important roles in regulating downstream components in calcium signaling pathways. In rice, the CDPKs constitute a large multigene family consisting of 29 genes, but the biological functions and functional divergence or redundancy of most of these genes remain unclear. Using a mini-scale full-length cDNA overexpressor (FOX) gene hunting system, we generated 250 independent transgenic rice plants overexpressing individual rice CDPKs (CDPK FOX-rice lines). These CDPK FOX-rice lines were screened for salt stress tolerance. The survival rate of the OsCPK21-FOX plants was higher than that of wild-type (WT) plants grown under high salinity conditions. The inhibition of seedling growth by abscisic acid (ABA) treatment was greater in the OsCPK21-FOX plants than in WT plants. Several ABA- and high salinity-inducible genes were more highly expressed in the OsCPK21-FOX plants than in WT plants. These results suggest that OsCPK21 is involved in the positive regulation of the signaling pathways that are involved in the response to ABA and salt stress.
Asunto(s)
Oryza/genética , Proteínas de Plantas/genética , Proteínas Quinasas/genética , Tolerancia a la Sal/genética , Ácido Abscísico/farmacología , Frío , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Oryza/enzimología , Oryza/crecimiento & desarrollo , Filogenia , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente , Proteínas Quinasas/clasificación , Proteínas Quinasas/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Tolerancia a la Sal/fisiología , Plantas Tolerantes a la Sal/genética , Cloruro de Sodio/farmacologíaRESUMEN
A simple, low-cost capillary electrophoresis-mass spectrometry (CE-MS) method is demonstrated for the simultaneous analysis of amino acids and small carboxylic acids (glycerate, lactate, fumarate, succinate, malate, tartrate, citrate, iso-citrate, cis-aconitate, and shikimate). All CE-MS experiments were performed using a single uncoated fused-silica capillary and with a single separation electrolyte, formic acid. For CE polarity, the CE inlet was set as the anode, and the MS side was set as the cathode. By using high-speed sheath gas flow, the apparent mobilities of all compounds were sped up; thus, the migration times of the carboxylic acids were reduced. In positive ion mode ESI-MS detection, small carboxylic acids were detected faintly as m/z = [M + 18](+) or [M + 23](+), after protonated molecule detection (m/z = [M + 1](+)) of the amino acids. In negative ion mode, all of these small carboxylic acids were detected clearly as deprotonated molecules (m/z = [M - 1](-)), after detection of the amino acids. By changing the polarity of the MS during CE separation, both amino acids and small carboxylic acids were detectable in a single electrophoresis analysis run. With this method, the diurnal metabolic changes of pineapple leaves were observed as reflecting Crassulacean acid metabolism.
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Aminoácidos/análisis , Ácidos Carboxílicos/análisis , Electroforesis Capilar/métodos , Espectrometría de Masas/métodos , Electrólitos , Electroforesis Capilar/instrumentación , Diseño de Equipo , Espectrometría de Masas/instrumentación , Dióxido de SilicioRESUMEN
Sucrose transporters (SUTs) are known to play critical roles in the uptake of sucrose from the apoplast in various steps of sugar translocation. Because developing pollen is symplastically isolated from anther tissues, it is hypothesized that SUTs are active in the uptake of apoplastic sucrose into pollen. To investigate this possibility, a comprehensive expression analysis was performed for members of the SUT gene family in the developing pollen of rice (Oryza sativa L.) using real-time RT-PCR combined with a laser microdissection technique. Among the five SUT genes, OsSUT1 and OsSUT3 were found to be preferentially expressed and had temporal expression patterns that were distinct from each other. Expression of OsSUT1 in pollen was confirmed by a promoter-GUS fusion assay. The physiological function of OsSUT1 in pollen was further investigated using retrotransposon insertion mutant lines. While the homozygote of disrupted OsSUT1 (SUT1-/-) could not be obtained, heterozygote plants (SUT1+/-) showed normal grain filling. Their progeny segregated into SUT1+/- and SUT1+/+ with the ratio of 1:1, suggesting that the pollen disrupted for OsSUT1 is dysfunctional. This hypothesis was reinforced in vivo by a backcross of SUT1+/- plants with wild-type plants and also by in vitro pollen germination on the artificial media. However, starch accumulation during pollen development was not affected by disruption of OsSUT1, suggesting that the sugar(s) required for starch biosynthesis is supplied by other sugar transporters.
Asunto(s)
Oryza , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Polen , Transporte Biológico/genética , Perfilación de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Proteínas de Transporte de Membrana/genética , Proteínas de Transporte de Membrana/metabolismo , Mutación , Oryza/genética , Oryza/crecimiento & desarrollo , Oryza/metabolismo , Polen/genética , Polen/crecimiento & desarrollo , Polen/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Almidón/metabolismoRESUMEN
In plants, glutamine synthetase (GS) is the enzyme that is mainly responsible for the assimilation of ammonium. Conversely, in microorganisms such as bacteria and Ascomycota, NADP(H)-dependent glutamate dehydrogenase (GDH) and GS both have important roles in ammonium assimilation. Here, we report the changes in nitrogen assimilation, metabolism, growth, and grain yield of rice plants caused by an ectopic expression of NADP(H)-GDH (gdhA) from the fungus Aspergillus niger in the cytoplasm. An investigation of the kinetic properties of purified recombinant protein showed that the fungal gdhA had 5.4-10.2 times higher V(max) value and 15.9-43.1 times higher K(m) value for NH(4)(+), compared with corresponding values for rice cytosolic GS as reported in the literature. These results suggested that the introduction of fungal GDH into rice could modify its ammonium assimilation pathway. We therefore expressed gdhA in the cytoplasm of rice plants. NADP(H)-GDH activities in the gdhA-transgenic lines were markedly higher than those in a control line. Tracer experiments by feeding with (15)NH(4)(+) showed that the introduced gdhA, together with the endogenous GS, directly assimilated NH(4)(+) absorbed from the roots. Furthermore, in comparison with the control line, the transgenic lines showed an increase in dry weight and nitrogen content when sufficient nitrogen was present, but did not do so under low-nitrogen conditions. Under field condition, the transgenic line examined showed a significant increase in grain yield in comparison with the control line. These results suggest that the introduction of fungal gdhA into rice plants could lead to better growth and higher grain yield by enhancing the assimilation of ammonium.
Asunto(s)
Proteínas Fúngicas/metabolismo , Glutamato Deshidrogenasa (NADP+)/metabolismo , Nitrógeno/metabolismo , Oryza/crecimiento & desarrollo , Oryza/metabolismo , Plantas Modificadas Genéticamente/crecimiento & desarrollo , Plantas Modificadas Genéticamente/metabolismo , Proteínas Fúngicas/genética , Glutamato Deshidrogenasa (NADP+)/genética , Oryza/genética , Plantas Modificadas Genéticamente/genéticaRESUMEN
Rice (Oryza sativa) is indispensable in the diet of most of the world's population. Thus, it is an important target in which to alter iron (Fe) uptake and homeostasis, so as to increase Fe accumulation in the grain. We previously isolated OsYSL2, a functional iron [Fe(II)]- and manganese [Mn(II)]-nicotianamine complex transporter that is expressed in phloem cells and developing seeds. We produced RNAi (OsYSL2i) and overexpression lines (OXOsYSL2) of OsYSL2. At the vegetative stage in an OsYSL2i line, the Fe and Mn concentrations were decreased in the shoots, and the Fe concentration was increased in the roots. At the reproductive stage, positron-emitting tracer imaging system analysis revealed that Fe translocation to the shoots and seeds was suppressed in OsYSL2i. The Fe and Mn concentrations were decreased in the seeds of OsYSL2i, especially in the endosperm. Moreover, the Fe concentration in OXOsYSL2 was lower in the seeds and shoots, but higher in the roots, compared with the wild type. Furthermore, when OsYSL2 expression was driven by the sucrose transporter promoter, the Fe concentration in the polished rice was up to 4.4-fold higher compared with the wild type. These results indicate that the altered expression of OsYSL2 changes the localization of Fe, and that OsYSL2 is a critical Fe-nicotianamine transporter important for Fe translocation, especially in the shoots and endosperm.