RESUMEN
The demand for rice is likely to increase approximately 1.5 times by the year 2050. In contrast, the rice production is stagnant since the past decade as the ongoing rice breeding program is unable to increase the production further, primarily because of the problem in grain filling. Investigations have revealed several reasons for poor filling of the grains in the inferior spikelets of the compact panicle, which are otherwise genetically competent to develop into well-filled grains. Among these, the important reasons are 1) poor activities of the starch biosynthesizing enzymes, 2) high ethylene production leading to inhibition in expressions of the starch biosynthesizing enzymes, 3) insufficient division of the endosperm cells and endoreduplication of their nuclei, 4) low accumulation of cytokinins and indole-3-acetic acid (IAA) that promote grain filling, and 5) altered expressions of the miRNAs unfavorable for grain filling. At the genetic level, several genes/QTLs linked to the yield traits have been identified, but the information so far has not been put into perspective toward increasing the rice production. Keeping in view the genetic competency of the inferior spikelets to develop into well-filled grains and based on the findings from the recent research studies, improving grain filling in these spikelets seems plausible through the following biotechnological interventions: 1) spikelet-specific knockdown of the genes involved in ethylene synthesis and overexpression of ß-CAS (ß-cyanoalanine) for enhanced scavenging of CN- formed as a byproduct of ethylene biosynthesis; 2) designing molecular means for increased accumulation of cytokinins, abscisic acid (ABA), and IAA in the caryopses; 3) manipulation of expression of the transcription factors like MYC and OsbZIP58 to drive the expression of the starch biosynthesizing enzymes; 4) spikelet-specific overexpression of the cyclins like CycB;1 and CycH;1 for promoting endosperm cell division; and 5) the targeted increase in accumulation of ABA in the straw during the grain filling stage for increased carbon resource remobilization to the grains. Identification of genes determining panicle compactness could also lead to an increase in rice yield through conversion of a compact-panicle into a lax/open one. These efforts have the ability to increase rice production by as much as 30%, which could be more than the set production target by the year 2050.
RESUMEN
The world's increase in rice (Oryza sativa L.) production is not keeping up with the increase in its population. To boost the introduction of new high-yielding cultivars, knowledge is being gained on the genes and quantitative trait loci (QTLs) determining the panicle phenotype. The important are those determining yield of the crop, such as grain numbers per panicle and size and weight of the grains. Biochemical and molecular functions of many of them are understood in some details. Among these, OsCKX2 and OsSPL14 have been shown to increase panicle branching and grain numbers when overexpressed. Furthermore, miRNAs appear to play an important role in determining the panicle morphology by regulating the expressions of the genes like OsSPL14 and GRF4 involved in panicle branching and grain numbers and length. Mutations also greatly influence the grain shape and size. However, the information gained so far on the genetic regulation of grain filling and panicle morphology has not been successfully put into commercial application. Furthermore, the identification of the gene(s)/QTLs regulating panicle compactness is still lacking, which may enable the researchers to convert a compact-panicle cultivar into a lax/open one, and thereby increasing the chances of enhancing the yield of a desired compact-panicle cultivar obtained by the breeding effort.
Asunto(s)
Oryza , Grano Comestible/genética , Regulación de la Expresión Génica de las Plantas/genética , Oryza/genética , Fitomejoramiento , Sitios de Carácter Cuantitativo/genéticaRESUMEN
The increase in much required rice production through breeding programmes is on decline. The primary reason being poor filling of grains in the basal spikelets of the heavy and compact panicle rice developed. These spikelets are genetically competent to develop into well filled grains, but fail to do so because the carbohydrate assimilates available to them remain unutilized, reportedly due to poor activities of the starch biosynthesizing enzymes, high production of ethylene leading to enhanced synthesis of the downstream signaling component RSR1 protein that inhibits GBSS1 activity, poor endosperm cell division and endoreduplication of the endosperm nuclei, altered expression of the transcription factors influencing grain filling, enhanced expression and phosphorylation of 14-3-3 proteins, poor expression of the seed storage proteins, reduced synthesis of the hormones like cytokinins and IAA that promote grain filling, and altered expression of miRNAs preventing their normal role in grain filling. Since the basal spikelets are genetically competent to develop into well filled mature grains, biotechnological interventions in terms of spikelet-specific overexpression of the genes encoding enzymes involved in grain filling and/or knockdown/overexpression of the genes influencing the activities of the starch biosynthesizing enzymes, various cell cycle events and hormone biosynthesis could increase rice production by as much as 30%, much more than the set production target of 800 mmt. Application of these biotechnological interventions in the heavy and compact panicle cultivars producing grains of desired quality would also maintain the quality of the grains having demand in market besides increasing the rice production per se.
Asunto(s)
Oryza , Grano Comestible/metabolismo , Endospermo , Oryza/genética , Oryza/metabolismo , Fitomejoramiento , Almidón/metabolismoRESUMEN
KEY MESSAGE: Drought stress response studies and overexpression of vun-miR408 proved it to be essential for abiotic stress tolerance in cowpea. Small RNA and transcriptome sequencing of an elite high-yielding drought-tolerant Indian cowpea cultivar, Pusa Komal revealed a differential expression of 198 highly conserved, 21 legume-specific, 14 less-conserved, and 10 novel drought-responsive microRNAs (miRNAs) along with 3391 (up-regulated) and 3799 (down-regulated) genes, respectively, in the leaf and root libraries. Among the differentially expressed miRNAs, vun-miR408-3p, showed an up-regulation of 3.53-log2-fold change under drought stress. Furthermore, laccase 12 (LAC 12) was identified as the potential target of vun-miR408-3p using 5' RNA ligase-mediated rapid amplification of cDNA ends. The stable transgenic cowpea lines overexpressing artificial vun-miR408-3p (OX-amiR408) displayed enhanced drought and salinity tolerance as compared to the wild-type plants. An average increase of 30.17% in chlorophyll, 26.57% in proline, and 27.62% in relative water content along with lesser cellular H2O2 level was observed in the transgenic lines in comparison with the wild-type plants under drought stress. Additionally, the scanning electron microscopic study revealed a decrease in the stomatal aperture and an increase in the trichome density in the transgenic lines. The expression levels of laccase 3 and laccase 12, the potential targets of miR408, related to lipid catabolic processes showed a significant reduction in the wild-type plants under drought stress and the transgenic lines, indicating the regulation of lignin content as a plausibly essential trait related to the drought tolerance in cowpea. Taken together, this study primarily focused on identification of drought-responsive miRNAs and genes in cowpea, and functional validation of role of miR408 towards drought stress response in cowpea.
Asunto(s)
Sequías , MicroARNs/genética , ARN de Planta/genética , Transcriptoma/genética , Vigna/fisiología , Perfilación de la Expresión Génica , MicroARNs/metabolismo , ARN de Planta/metabolismo , Análisis de Secuencia de ARNRESUMEN
The Teosinte branched 1/Cycloidea/Proliferating cell factor (TCP) transcription factors are potent growth and developmental regulators in plants, also responsive to various hormonal and environmental stimuli. In this study, we primarily focused on the functional role of TCP9, a nuclear-localised Class-I TCP transcription factor in a drought and heat-tolerant legume crop, cowpea (Vigna unguiculata). Under drought stress, a higher protein expression level of TCP9 was observed in the leaves of the drought-tolerant cowpea cultivar Pusa Komal as compared to the drought-sensitive cultivar TVu-7778. Further, overexpression of VuTCP9 resulted in reduced cell and stomata size, aperture length and width while cell and overall stomatal density in the 35S::VuTCP9 transgenic cowpea lines increased. Phenotypic alterations, such as reduced leaf size and vigour, altered seed coats displaying extension pattern similar to the 'Watson pattern' and delayed senescence were prominent in the transgenic lines. Under normal conditions, the gas exchange and fluorescence measurements indicated reduction in transpiration rate (E), stomatal conductance (gs ) and photosynthetic efficiency (Φ PSII). However, water usage efficiency (WUE) remained unaltered in the transgenic lines as compared to the wild-type (WT) plants. Furthermore, the transgenic lines displayed higher tolerance to oxidative, drought and salinity stress, maintained relatively higher relative water content and lower occurrence of H2 O2 , as compared to the WT plants. Genes related to the jasmonic acid biosynthesis, stomatal development and abiotic stress responsiveness, such as TTG1, NAC25, SPCH and GRP1, increased and LOX2 decreased significantly in the transgenic lines.
Asunto(s)
Sequías , Vigna , Regulación de la Expresión Génica de las Plantas , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente/genética , Tolerancia a la Sal/fisiología , Estrés Fisiológico , Vigna/genética , Vigna/metabolismoRESUMEN
This review article summarises the role of membrane transporters and their regulatory kinases in minimising the toxicity of Na+ in the plant under salt stress. The salt-tolerant plants keep their cytosolic level of Na+ up to 10-50mM. The first line of action in this context is the generation of proton motive force by the plasma membrane H+-ATPase. The generated proton motive force repolarises the membrane that gets depolarised due to passive uptake of Na+ under salt stress. The proton motive force generated also drives the plasma membrane Na+/H+ antiporter, SOS1 that effluxes the cytosolic Na+ back into the environment. At the intracellular level, Na+ is sequestered by the vacuole. Vacuolar Na+ uptake is mediated by Na+/H+ antiporter, NHX, driven by the electrochemical gradient for H+, generated by tonoplast H+ pumps, both H+ATPase and PPase. However, it is the expression of the regulatory kinases that make these transporters active through post-translational modification enabling them to effectively manage the cytosolic level of Na+, which is essential for tolerance to salinity in plants. Yet our knowledge of the expression and functioning of the regulatory kinases in plant species differing in tolerance to salinity is scant. Bioinformatics-based identification of the kinases like OsCIPK24 in crop plants, which are mostly salt-sensitive, may enable biotechnological intervention in making the crop cultivar more salt-tolerant, and effectively increasing its annual yield.
Asunto(s)
Proteínas de Transporte de Membrana , Tolerancia a la Sal , Plantas Tolerantes a la Sal , Intercambiadores de Sodio-Hidrógeno , VacuolasRESUMEN
Plant's response to fresh- and saline-water flooding and the resulting partial submergence, seems different due to the added complexities of element toxicity of salinity. We identified a few rice genotypes which can tolerate combined stresses of partial submergence and salinity during saline water flooding. To gain mechanistic insights, we compared two rice genotypes: Varshadhan (freshwater-flooding tolerant) and Rashpanjor (both fresh- and saline-water flooding tolerant). We found greater ethylene production and increased "respiratory burst oxidase homolog" (RBOH)-mediated reactive oxygen species (ROS) production led to well-developed constitutive aerenchyma formation in Rashpanjor, which makes it preadapted to withstand fresh- and saline-water flooding. On the contrary, an induced aerenchyma formation-dependent tolerance mechanism of Varshadhan worked well for freshwater flooding but failed to provide tolerance to saline-water flooding. Additional salt stress was found to significantly inhibit the induced aerenchyma formation process due to the dampening of ROS signaling by the action of metallothionein in Varshadhan. Besides, inconspicuous changes in ionic regulation processes in these two genotypes under saline-water flooding suggest preadapted constitutive aerenchyma formation plays a more significant role than elemental toxicity per se in tolerating combined stresses encountered during saline water flooding in rice. Overall, our study indicated that well-developed constitutive aerenchyma provide an adaptive advantage during partial submergence due to saline water flooding in rice as the key process of induced aerenchyma formation is hampered in the presence of salinity stress coupled with partial submergence.
Asunto(s)
Oryza , Inundaciones , Oryza/genética , Raíces de Plantas , Especies Reactivas de Oxígeno , Aguas SalinasRESUMEN
High grain number is positively correlated with grain yield in rice, but it is compromised because of poor filling of basal spikelets in dense panicle bearing numerous spikelets. The phenomenon that turns the basal spikelets of compact panicle sterile in rice is largely unknown. In order to understand the factor(s) that possibly determines such spikelet sterility in compact panicle cultivars, QTLs and candidate genes were identified for spikelet fertility and associated traits like panicle compactness, and ethylene production that significantly influences the grain filling using recombinant inbred lines developed from a cross between indica rice cultivars, PDK Shriram (compact, high spikelet number) and Heera (lax, low spikelet number). Novel QTLs, qSFP1.1, qSFP3.1, and qSFP6.1 for spikelet fertility percentage; qIGS3.2 and qIGS4.1 for panicle compactness; and qETH1.2, qETH3.1, and qETH4.1 for ethylene production were consistently identified in both kharif seasons of 2017 and 2018. The comparative expression analysis of candidate genes like ERF3, AP2-like ethylene-responsive transcription factor, EREBP, GBSS1, E3 ubiquitin-protein ligase GW2, and LRR receptor-like serine/threonine-protein kinase ERL1 associated with identified QTLs revealed their role in poor grain filling of basal spikelets in a dense panicle. These candidate genes thus could be important for improving grain filling in compact-panicle rice cultivars through biotechnological interventions.
Asunto(s)
Oryza/genética , Proteínas de Plantas/genética , Sitios de Carácter Cuantitativo , Semillas/genética , Fertilidad/genéticaRESUMEN
Development of rice cultivars bearing numerous spikelets by breeding approach to increase the yearly production of rice to approximately 800 million metric tons to feed the ever increasing population of the world accompanies poor grain filling in the inferior spikelets preventing achievement of the yield potential. As the initial stages of caryopses development are of much importance for grain filling, spatio-temporal expressions of the miRNAs were studied during these periods in the spikelets of a compact-panicle rice cultivar, Oryza sativa cv. Mahalaxmi, bearing numerous spikelets per panicle to understand the reason of poor grain filling at the level of the initial biochemical events. Differential expression of several known miRNAs between the superior and inferior spikelets suggested great difference in metabolism related to grain filling in the spikelets based on their spatial location on compact panicle. Expressions of five known and four novel miRNAs were validated by Northern. Their targets included the enzymes directly involved in starch biosynthesis like sucrose synthase, starch synthase and pullulanase, besides others. Spatio-temporal expression studies of these miRNAs in the spikelets of Mahalaxmi revealed a pattern of mostly a greater expression in the inferior spikelets compared with the superior ones concomitant with an inverse expression of the target genes, which was not observed in the lax-panicle cultivar Upahar. The study thus revealed that the grain filling in rice is greatly regulated by miRNAs, and these miRNAs or their target genes could be considered for biotechnological interventions for improving grain filling in the rice cultivars of interest.
Asunto(s)
Grano Comestible , Regulación de la Expresión Génica de las Plantas , MicroARNs , Oryza , Proteínas de Plantas , Grano Comestible/genética , Grano Comestible/crecimiento & desarrollo , Grano Comestible/metabolismo , Perfilación de la Expresión Génica , MicroARNs/genética , Oryza/genética , Oryza/crecimiento & desarrollo , Fitomejoramiento , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismoRESUMEN
Soil salinization is a serious problem for cultivation of rice, as among cereals rice is the most salt sensitive crop, and more than 40% of the total agricultural land amounting to approximately 80 million ha the world over is salt affected. Salinity affects a plant in a varieties of ways, including ion toxicity, osmotic stress and oxidative damage. Since miRNAs occupy the top place in biochemical events determining a trait, understanding their role in salt tolerance is highly desirable, which may allow introduction of the trait in the rice cultivars of choice through biotechnological interventions. High throughput sequencing of sRNAs in the root and shoot tissues of the seedlings of the control and NaCl treated Pokkali, a salt-tolerant rice variety, identified 75 conserved miRNAs and mapped 200 sRNAs to the rice genome as novel miRNAs. Expression of nine novel miRNAs and two conserved miRNAs were confirmed by Northern blotting. Several of both conserved and novel miRNAs that expressed differentially in root and/or shoot tissues targeted transcription factors like AP2/EREBP domain protein, ARF, NAC, MYB, NF-YA, HD-Zip III, TCP and SBP reported to be involved in salt tolerance or in abiotic stress tolerance in general. Most of the novel miRNAs expressed in the salt tolerant wild rice Oryza coarctata, suggesting conservation of miRNAs in taxonomically related species. One of the novel miRNAs, osa-miR12477, also targeted L-ascorbate oxidase (LAO), indicating build-up of oxidative stress in the plant upon salt treatment, which was confirmed by DAB staining. Thus, salt tolerance might involve miRNA-mediated regulation of 1) cellular abundance of the hormone signaling components like EREBP and ARF, 2) synthesis of abiotic stress related transcription factors, and 3) antioxidative component like LAO for mitigation of oxidative damage. The study clearly indicated importance of osa-miR12477 regulated expression of LAO in salt tolerance in the plant.
Asunto(s)
MicroARNs/genética , Oryza/genética , Tolerancia a la Sal/genética , Northern Blotting/métodos , Regulación de la Expresión Génica de las Plantas/genética , Secuenciación de Nucleótidos de Alto Rendimiento/métodos , Estrés Oxidativo/genética , Salinidad , Plantones/genética , Estrés Fisiológico/genética , Factores de Transcripción/genéticaRESUMEN
Shortfall of rain that creates drought like situation in non-irrigated agriculture system often limits rice production, necessitating introduction of drought tolerance trait into the cultivar of interest. The mechanism governing drought tolerance is, however, largely unknown, particularly the involvement of miRNAs, the master regulators of biochemical events. In this regard, response study on a drought tolerant rice variety KMJ 1-12-3 to 20% PEG (osmolality- 315 mOsm/kg) as drought stress revealed significant changes in abundance of several conserved miRNAs targeting transcription factors like homeodomain-leucine zipper, MADS box family protein, C2H2 zinc finger protein and Myb, well known for their importance in drought tolerance in plants. The response study also revealed significant PEG-induced decrease in abundance of the miRNAs targeting cyclin A, cyclin-dependent kinase, guanine nucleotide exchange factor, GTPase-activating protein, 1-aminocyclopropane-1-carboxylic acid oxidase and indole-3-acetic beta-glucosyl transferase indicating miRNA-regulated role of the cell cycle regulators, G-protein signalling and the plant hormones ethylene and IAA in drought tolerance in plants. The study confirmed the existence of four novel miRNAs, including osa-miR12470, osa-miR12471, osa-miR12472 and osa-miR12473, and the targets of three of them could be successfully validated. The PEG-induced decrease in abundance of the novel miRNAs osa-miR12470 and osa-miR12473 targeting RNA dependent RNA polymerase and equilibrative nucleoside transporter, respectively suggested an overall increase in both degradation and synthesis of nucleic acids in plants challenged with drought stress. The drought-responsive miRNAs identified in the study may be proved useful in introducing the trait in the rice cultivars of choice by manipulation of their cellular abundance.
Asunto(s)
Sequías , Regulación de la Expresión Génica de las Plantas , MicroARNs/genética , Oryza/fisiología , Proteínas de Plantas/genética , Northern Blotting , Etilenos/metabolismo , Oryza/genética , Reproducibilidad de los Resultados , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de Transcripción/genéticaRESUMEN
BACKGROUND: Poor filling of grains in the basal spikelets of large size panicles bearing numerous spikelets has been a major limitation in attempts to increase the rice production to feed the world's increasing population. Considering that biotechnological intervention could play important role in overcoming this limitation, the role of cytokinin in grain filling was investigated based on the information on cell proliferating potential of the hormone and reports of its high accumulation in immature seeds. RESULTS: A comparative study considering two rice varieties differing in panicle compactness, lax-panicle Upahar and compact-panicle OR-1918, revealed significant difference in grain filling, cytokinin oxidase (CKX) activity and expression, and expression of cell cycle regulators and cytokinin signaling components between the basal and apical spikelets of OR-1918, but not of Upahar. Exogenous application of cytokinin (6-Benzylaminopurine, BAP) to OR-1918 improved grain filling significantly, and this was accompanied by a significant decrease in expression and activity of CKX, particularly in the basal spikelets where the activity of CKX was significantly higher than that in the apical spikelets. Cytokinin application also resulted in significant increase in expression of cell cycle regulators like cyclin dependent kinases and cyclins in the basal spikelets that might be facilitating cell division in the endosperm cells by promoting G1/S phase and G2/M phase transition leading to improvement in grain filling. Expression studies of type-A response regulator (RR) component of cytokinin signaling indicated possible role of OsRR3, OsRR4 and OsRR6 as repressors of CKX expression, much needed for an increased accumulation of CK in cells. Furthermore, the observed effect of BAP might not be solely because of it, but also because of induced synthesis of trans-zeatin (tZ) and N6-(Δ2-isopentenyl)adenine (iP), as reflected from accumulation of tZR (tZ riboside) and iPR (iP riboside), and significantly enhanced expression of an isopentenyl transferase (IPT) isoform. CONCLUSION: The results suggested that seed-specific overexpression of OsRR4 and OsRR6, and more importantly of IPT9 could be an effective biotechnological intervention towards improving the CK level of the developing caryopses leading to enhanced grain filling in rice cultivars bearing large panicles with numerous spikelets, and thereby increasing their yield potential.
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Citocininas/farmacología , Grano Comestible/efectos de los fármacos , Oryza/efectos de los fármacos , Compuestos de Bencilo/farmacología , Recuento de Células , Grano Comestible/crecimiento & desarrollo , Grano Comestible/metabolismo , Endospermo/citología , Endospermo/efectos de los fármacos , Endospermo/crecimiento & desarrollo , Endospermo/ultraestructura , Citometría de Flujo , Oryza/crecimiento & desarrollo , Oryza/metabolismo , Oryza/ultraestructura , Oxidorreductasas/metabolismo , Purinas/farmacología , TranscriptomaRESUMEN
Although salt tolerance is a feature representative of halophytes, most studies on this topic in plants have been conducted on glycophytes. Transcriptome profiles are also available for only a limited number of halophytes. Hence, the present study was conducted to understand the molecular basis of salt tolerance through the transcriptome profiling of the halophyte Suaeda maritima, which is an emerging plant model for research on salt tolerance. Illumina sequencing revealed 72,588 clustered transcripts, including 27,434 that were annotated using BLASTX. Salt application resulted in the 2-fold or greater upregulation of 647 genes and downregulation of 735 genes. Of these, 391 proteins were homologous to proteins in the COGs (cluster of orthologous groups) database, and the majorities were grouped into the poorly characterized category. Approximately 50% of the genes assigned to MapMan pathways showed homology to S. maritima. The majority of such genes represented transcription factors. Several genes also contributed to cell wall and carbohydrate metabolism, ion relation, redox responses and G protein, phosphoinositide and hormone signaling. Real-time PCR was used to validate the results of the deep sequencing for the most of the genes. This study demonstrates the expression of protein kinase C, the target of diacylglycerol in phosphoinositide signaling, for the first time in plants. This study further reveals that the biochemical and molecular responses occurring at several levels are associated with salt tolerance in S. maritima. At the structural level, adaptations to high salinity levels include the remodeling of cell walls and the modification of membrane lipids. At the cellular level, the accumulation of glycinebetaine and the sequestration and exclusion of Na+ appear to be important. Moreover, this study also shows that the processes related to salt tolerance might be highly complex, as reflected by the salt-induced enhancement of transcription factor expression, including hormone-responsive factors, and that this process might be initially triggered by G protein and phosphoinositide signaling.
RESUMEN
Breeding programs for increasing spikelet number in rice have resulted in compactness of the panicle, accompanied by poor grain filling in inferior spikelets. Although the inefficient utilization of assimilate has been indicated as responsible for this poor grain filling, the underlying cause remains elusive. The current study utilized the suppression subtractive hybridization technique to identify 57 and 79 genes that overexpressed in the superior and inferior spikelets (with respect to each other), respectively, of the compact-panicle rice cultivar Mahalaxmi. Functional categorization of these differentially expressed genes revealed a marked metabolic difference between the spikelets according to their spatial location on the panicle. The expression of genes encoding seed storage proteins was dominant in inferior spikelets, whereas genes encoding regulatory proteins, such as serine-threonine kinase, zinc finger protein and E3 ligase, were highly expressed in superior spikelets. The expression patterns of these genes in the inferior and superior spikelets of Mahalaxmi were similar to those observed in another compact-panicle cultivar, OR-1918, but differed from those obtained in two lax-panicle cultivars, Upahar and Lalat. The results first suggest that the regulatory proteins abundantly expressed in the superior spikelets of compact-panicle cultivars and in both the superior and inferior spikelets of lax-panicle cultivars but poorly expressed in the inferior spikelets of compact-panicle cultivars promote grain filling. Second, the high expression of seed-storage proteins observed in the inferior spikelets of compact-panicle cultivars appears to inhibit the grain filling process. Third, the low expression of enzymes of the Krebs cycle in inferior spikelets compared with superior spikelets of compact-panicle cultivars is bound to lead to poor ATP generation in the former and consequently limit starch biosynthesis, an ATP-consuming process, resulting in poor grain filling.
Asunto(s)
Genes de Plantas , Oryza/genética , Adenosina Trifosfato/metabolismo , Ciclo del Ácido Cítrico/genética , ADN Complementario/genética , ADN de Plantas/genética , Grano Comestible/genética , Grano Comestible/metabolismo , Etiquetas de Secuencia Expresada , Regulación de la Expresión Génica de las Plantas , Oryza/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , ARN de Planta/genética , Proteínas de Almacenamiento de Semillas/genética , Proteínas de Almacenamiento de Semillas/metabolismo , Técnicas de Hibridación Sustractiva , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
BACKGROUND: Although miRNAs are reportedly involved in the salt stress tolerance of plants, miRNA profiling in plants has largely remained restricted to glycophytes, including certain crop species that do not exhibit any tolerance to salinity. Hence, this manuscript describes the results from the miRNA profiling of the halophyte Suaeda maritima, which is used worldwide to study salt tolerance in plants. RESULTS: A total of 134 conserved miRNAs were identified from unique sRNA reads, with 126 identified using miRBase 21.0 and an additional eight identified using the Plant Non-coding RNA Database. The presence of the precursors of seven conserved miRNAs was validated in S. maritima. In addition, 13 novel miRNAs were predicted using the ESTs of two mangrove plants, Rhizophora mangle and Heritiera littoralis, and the precursors of seven miRNAs were found in S. maritima. Most of the miRNAs considered for characterization were responsive to NaCl application, indicating their importance in the regulation of metabolic activities in plants exposed to salinity. An expression study of the novel miRNAs in plants of diverse ecological and taxonomic groups revealed that two of the miRNAs, sma-miR6 and sma-miR7, were also expressed in Oryza sativa, whereas another two, sma-miR2 and sma-miR5, were only expressed in plants growing under the influence of seawater, similar to S. maritima. CONCLUSION: The distribution of conserved miRNAs among only 25 families indicated the possibility of identifying a greater number of miRNAs with increase in knowledge of the genomes of more halophytes. The expression of two novel miRNAs, sma-miR2 and sma-miR5, only in plants growing under the influence of seawater suggested their metabolic regulatory roles specific to saline environments, and such behavior might be mediated by alterations in the expression of certain genes, modifications of proteins leading to changes in their activity and production of secondary metabolites as revealed by the miRNA target predictions. Moreover, the auxin responsive factor targeted by sma-miR7 could also be involved in salt tolerance because the target is conserved between species. This study also indicated that the transcriptome of one species can be successfully used to computationally predict the miRNAs in other species, especially those that have similar metabolism, even if they are taxonomically separated.
Asunto(s)
Chenopodiaceae/genética , Malvaceae/genética , MicroARNs/genética , ARN de Planta/genética , Rhizophoraceae/genética , Tolerancia a la Sal , Chenopodiaceae/metabolismo , Biología Computacional , Etiquetas de Secuencia Expresada , Regulación de la Expresión Génica de las Plantas , Secuenciación de Nucleótidos de Alto Rendimiento , Malvaceae/metabolismo , MicroARNs/metabolismo , Oryza/efectos de los fármacos , Oryza/genética , Oryza/metabolismo , ARN de Planta/metabolismo , Rhizophoraceae/metabolismo , Plantas Tolerantes a la Sal/genética , Plantas Tolerantes a la Sal/metabolismo , Cloruro de Sodio/farmacología , TranscriptomaRESUMEN
To look into a possible involvement of plasma membrane H+ATPase (PM-H+ATPase, EC 3.6.3.6) in mitigation of physiological disturbances imposed by salt stress, response of the enzyme was studied in two Oryza sativa Indica cultivars, salt-tolerant Lunishri and non-tolerant Badami, and a natural halophyte Suaeda maritima after challenge of the young plants with NaCl. Significant increase in activity of the enzyme was observed in response to NaCl in all the test plants with S. maritima showing maximum increase. Protein blot analysis, however, did not show any increase in the amount of the enzyme (protein). RNA blot analysis, on the other hand, revealed significant increase in transcript level of the enzyme upon NaCl treatment. In the rice cultivars, salt treatment also induced expression of a new isoform of PM-H+ATPase gene, not reported so far. The induced transcript showed maximum homology to OSA7 (O. sativa PM-H+ATPase isoform 7). Similar transcript message, however, remained constitutively present in S. maritima, along with the transcript of another isoform of PM-H+ATPase showing resemblance to OSA3 (O. sativa PM-H+ATPase isoform 3). The latter was the only PM-H+ATPase isoform expressed in both the rice cultivars not exposed to NaCl. In the salt-treated test plants, both rice and S. maritima, the salt-inducible PM-H+ATPase isoform resembling OSA7 was expressed in much greater amount than that resembling OSA3. Appearance of a new PM-H+ATPase transcript, besides increase in the enzyme activity, indicates the important role of the enzyme in maintaining ion-homeostasis in plants under salt stress, enabling them to survive under saline conditions.