Manling Wang

A novel rice calmodulin-like gene, OsMSR2, enhances drought and salt tolerance and increases ABA sensitivity in Arabidopsis

Many abiotic stimuli, such as drought and salt stresses, elicit changes in intracellular calcium levels that serve to convey information and activate adaptive responses. Ca2+ signals are perceived by different Ca2+ sensors, and calmodulin (CaM) is one of the best-characterized Ca2+ sensors in eukaryotes. Calmodulin-like (CML) proteins also exist in plants, but their functions at the physiological and molecular levels are largely unknown. In this report, we present data on OsMSR2 (Oryza sativa L. Multi-Stress-Responsive gene 2), a novel calmodulin-like protein gene isolated from rice Pei’ai 64S (Oryza sativa L.). Expression of OsMSR2 was strongly up-regulated by a wide spectrum of stresses, including cold, drought, and heat in different tissues at different developmental stages of rice, as revealed by both microarray and quantitative real-time RT-PCR analyses. Analysis of the recombinant OsMSR2 protein demonstrated its potential ability to bind Ca2+ in vitro. Expression of OsMSR2 conferred enhanced tolerance to high salt and drought in Arabidopsis (Arabidopsis thaliana) accompanied by altered expression of stress/ABA-responsive genes. Transgenic plants also exhibited hypersensitivity to ABA during the seed germination and post-germination stages. The results suggest that expression of OsMSR2 modulated salt and drought tolerance in Arabidopsis through ABA-mediated pathways.

OsSGL, a Novel DUF1645 Domain-Containing Protein, Confers Enhanced Drought Tolerance in Transgenic Rice and Arabidopsis

Drought is a major environmental factor that limits plant growth and crop productivity. Genetic engineering is an effective approach to improve drought tolerance in various crops, including rice (Oryza sativa). Functional characterization of relevant genes is a prerequisite when identifying candidates for such improvements. We investigated OsSGL (Oryza sativa Stress tolerance and Grain Length), a novel DUF1645 domain-containing protein from rice. OsSGL was up-regulated by multiple stresses and localized to the nucleus. Transgenic plants over-expressing or hetero-expressing OsSGL conferred significantly improved drought tolerance in transgenic rice and Arabidopsis thaliana, respectively. The overexpressing plants accumulated higher levels of proline and soluble sugars but lower malondialdehyde (MDA) contents under osmotic stress. Our RNA-sequencing data demonstrated that several stress-responsive genes were significantly altered in transgenic rice plants. We unexpectedly observed that those overexpressing rice plants also had extensive root systems, perhaps due to the altered transcript levels of auxin- and cytokinin-associated genes. These results suggest that the mechanism by which OsSGL confers enhanced drought tolerance is due to the modulated expression of stress-responsive genes, higher accumulations of osmolytes, and enlarged root systems.

Expression of OsMSR3 in Arabidopsis enhances tolerance to cadmium stress

Cadmium (Cd) is a widespread heavy metal released in the environment as a result of rock mineralization and of anthropogenic activities. Cadmium is highly toxic to human health and animals, and it is urgent to remove cadmium from the environment. A multiple stress responsive gene, OsMSR3, from rice (Oryza sativa (L.)), a member of class I sHSP family, has been previously noted to be induced by cold, drought, and heat stresses. In this study, quantitative RT-PCR (qRT-PCR) analysis revealed that OsMSR3 was also induced by Cd stress. Transgenic Arabidopsis expressing OsMSR3 showed enhanced tolerance to Cd, displaying longer roots, higher survival rates and accumulated more Cd, phytochelatins (PCs), non-protein thiol (NPT) and glutathione (GSH) than wild type plants under Cd condition. Expression of OsMSR3 conferred enhanced tolerance to Cd in Arabidopsis (thaliana (L.), Heynh.) accompanied by improving expressions of bHLH transcription factors and Cd stress-related genes. Taken together, our results suggested that expression of OsMSR3 in Arabidopsis enhanced tolerance to Cd stress, and OsMSR3 may act as a positive regulator of Cd stress tolerance in plants.

OsSGL , a novel pleiotropic stress-related gene enhances grain length and yield in rice

Abiotic stress seriously affects the yield of rice (Oryza sativa L.). Grain yield in rice is multiplicatively determined by the number of panicles, number of grains per panicle, and grain weight. Here, we describe the molecular and functional characterization of STRESS_tolerance and GRAIN_LENGTH (OsSGL), a rice gene strongly up-regulated by a wide spectrum of abiotic stresses. OsSGL encodes a putative member of the DUF1645 protein family of unknown function. Overexpression of OsSGL significantly altered certain development processes greatly and positively affecting an array of traits in transgenic rice plants, including increased grain length, grain weight and grain number per panicle, resulting in a significant increase in yield. Microscopical analysis showed that the enhanced OsSGL expression promoted cell division and grain filling. Microarray and quantitative real-time PCR (qRT-PCR) analyses revealed that a large number of genes involved in stress-response, cell cycle and cytokinin signaling processes were induced or suppressed in OsSGL-overexpressing plants. Together, our results suggest that OsSGL may regulate stress-tolerance and cell growth by acting via a cytokinin signaling pathway. This study not only contributes to our understanding of the underlying mechanism regulating rice stress-tolerance and grain length, but also provides a strategy for tailor-made crop yield improvement.

Overexpression of a novel MYB-related transcription factor, OsMYBR1 , confers improved drought tolerance and decreased ABA sensitivity in rice

The MYB proteins play important roles in regulating plant responses to environmental stresses. We cloned and functionally characterized a novel MYB-related gene, OsMYBR1, from rice. Our microarray and qRT-PCR analyses showed that its expression was induced by drought and cold in different tissues at various developmental stages. This gene encodes a putative MYB-related protein of 463 amino acid residues. Compared with wild-type (WT) plants, transgenic plants over-expressing OsMYBR1 exhibited much greater tolerance to drought stress and decreased sensitivity to abscisic acid (ABA). Under drought treatment, levels of free proline and soluble sugar were higher in transgenic plants than in the WT. Furthermore, transcriptional expression of four stress-related genes -- OsP5CS1, OsProt, OsLEA3, and OsRab16 -- was significantly increased in transgenic plants under drought stressed conditions and ABA. Our results provide evidence that OsMYBR1 is involved in mediating plant responses to ABA and drought.

Expression of rice gene OsMSR4 confers decreased ABA sensitivity and improved drought tolerance in Arabidopsis thaliana

Abstract The small heat shock proteins (sHSPs) are most prevalent in plants and are believed to play an important role in stress tolerance. Our microarray and qRT-PCR analyses of rice plants showed that the gene Oryza sativa Multi-Stress-Responsive 4 (OsMSR-4) is induced by heat, drought, and cold in different tissues at various developmental stages. OsMSR-4 encodes a Class III sHSP. Its expression in Arabidopsis thaliana conferred enhanced tolerance to drought accompanied by altered expression of other stress-related genes. Under drought conditions, levels of free proline were higher in transgenic plants than in the wild-type. The transgenics also showed decreased sensitivity to abscisic acid (ABA) during the seed germination and post-germination stages. Our study provides evidence that OsMSR4 has a key role in regulating plant responses to ABA and drought.

OsMsr9, a novel putative rice F-box containing protein, confers enhanced salt tolerance in transgenic rice and Arabidopsis

Salinity is a major environmental stress that limits agricultural production and geographical distribution of plants. In a previous study, it has been shown that OsMsr9 was induced by cold, drought and heat stresses. However, functions of OsMsr9 at physiological and molecular levels are still unknown. Here, we report that OsMsr9 plays roles in salt tolerance in plants. Quantitative real-time PCR (qPCR) analysis revealed that OsMsr9 was also rapidly and strongly induced by salt stress. Overexpression of OsMsr9 in Arabidopsis and rice showed enhanced salt stress tolerance displaying increased shoot and root elongation, higher survival rates in transgenic plants compared with wild type. OsMsr9 might act as a positive regulator of plant salt tolerance with reinforced expression of stress-related genes, such as RD29A, DREB2A and RAB18 in transgenic plants under salt conditions. Furthermore, transgenic plants accumulated more compatible solutes (proline and soluble sugar) and low level of malondialdehyde, alleviating the changes in reactive oxygen species. These results indicate that OsMsr9 could be a useful gene in developing transgenic crops with enhanced salt tolerance.

OsDSR-1, a calmodulin-like gene, improves drought tolerance through scavenging of reactive oxygen species in rice (Oryza sativa L.)

Calmodulin-like (CML) genes regulate plant growth, development, and responses to abiotic stresses such as salinity and drought. Many genes encoding CML proteins have been identified from rice (Oryza sativa), but their functions remain largely unknown. Our characterization of one putative CML gene, OsDSR-1 (O. sativa Drought Stress Response-1), showed that its protein binds Ca2+ and displays Ca2+-dependent conformational changes. In contrast to wild-type (WT) and OsDSR-1-RNA interference (OsDSR-1-Ri) plants, transgenic rice plants that overexpress OsDSR-1 were significantly more drought tolerant and had increased sensitivity to abscisic acid. Furthermore, their concentrations of free proline and soluble sugars and the activities of reactive oxygen species-scavenging enzymes as well as the transcript levels of many ROS-scavenging and stress-related genes were significantly enhanced under drought stress. Much less hydrogen peroxide and malondialdehyde accumulated in OsDSR-1-overexpressing (OsDSR-1-OE) plants than in either the Ri or WT plants. All of these results suggest that OsDSR-1 plays important roles in conferring tolerance to drought in rice by decreasing the occurrence of oxidative damage.

OsDSSR1, a novel small peptide, enhances drought tolerance in transgenic rice

Small signaling peptides play important roles in plant development and responses to abiotic and biotic stresses. We have identified a novel small peptide gene in rice, OsDSSR1, which is expressed mainly in the root, stem, node, leaf, and panicle. OsDSSR1 expression is also induced by drought, salinity, ABA, and H2O2 treatment. OsDSSR1 is localized in the nucleus and cytoplasm. Transgenic plants overexpressing OsDSSR1 exhibited enhanced drought stress tolerance and decreased ABA sensitivity as compared to the wild type. Overexpression of OsDSSR1 promoted the accumulation of compatible osmolytes, such as free proline and soluble sugars. OsDSSR1-overexpressing plants displayed enhanced OsSodCc2 and OscAPX expression and superoxide dismutase and ascorbate peroxidase activities under drought stress. RNA-sequencing data revealed that the expression of 72 abiotic stress-responsive genes was significantly altered in homozygous transgenic plants. These stress-responsive candidate genes will aid in expanding our understanding of the mechanisms by which small peptides mediate tolerance in crop species.

Expression of sorghum gene SbSGL enhances grain length and weight in rice

Grain weight is a major determining factor of rice (Oryza sativa L.) yield and the comprehensive embodiment of grain length, width, and thickness. Here, we describe the molecular and functional characterization of SbSGL (Sorghumbicolor L. stress tolerance and grain length), a sorghum gene that encodes a putative member of the DUF1645 protein family of unknown function. Expression of SbSGL in rice promoted cell division and grain filling, which affected an array of traits of rice, including grain length, grain weight, and seed setting rate. Expression of SbSGL also affected the expression of genes related to the plant cell cycle and grain size.