Xiaolan He

Impact of Metal and Metal Oxide Nanoparticles on Plant: A Critical Review

An increasing need of nanotechnology in various industries may cause a huge environment dispersion of nanoparticles in coming years. A concern about nanoparticles interaction with flora and fauna is raised due to a growing load of it in the environment. In recent years, several investigators have shown impact of nanoparticles on plant growth and their accumulation in food source. This review examines the research performed in the last decade to show how metal and metal oxide nanoparticles are influencing the plant metabolism. We addressed here, the impact of nanoparticle on plant in relation to its size, concentration, and exposure methodology. Based on the available reports, we proposed oxidative burst as a general mechanism through which the toxic effects of nanoparticles are spread in plants. This review summarizes the current understanding and the future possibilities of plant-nanoparticle research.

Applying hyperspectral imaging to explore natural plant diversity towards improving salt stress tolerance.

Salinity represents an abiotic stress constraint affecting growth and productivity of plants in many regions of the world. One of the possible solutions is to improve the level of salt resistance using natural genetic variability within crop species. In the context of recent knowledge on salt stress effects and mechanisms of salt tolerance, this review present useful phenomic approach employing different non-invasive imaging systems for detection of quantitative and qualitative changes caused by salt stress at the plant and canopy level. The focus is put on hyperspectral imaging technique, which provides unique opportunities for fast and reliable estimate of numerous characteristics associated both with various structural, biochemical and physiological traits. The method also provides possibilities to combine plant and canopy analyses with a direct determination of salinity in soil. The future perspectives in salt stress applications as well as some limits of the method are also identified.

A Novel Soybean Intrinsic Protein Gene, GmTIP2;3, Involved in Responding to Osmotic Stress

Water is essential for plant growth and development. Water deficiency leads to loss of yield and decreased crop quality. To understand water transport mechanisms in plants, we cloned and characterized a novel tonoplast intrinsic protein (TIP) gene from soybean with the highest similarity to TIP2-type from other plants, and thus designated GmTIP2;3. The protein sequence contains two conserved NPA motifs and six transmembrane domains. The expression analysis indicated that this gene was constitutively expressed in all detected tissues, with higher levels in the root, stem and pod, and the accumulation of GmTIP2;3 transcript showed a significant response to osmotic stresses, including 20% PEG6000 (polyethylene glycol) and 100 μM ABA (abscisic acid) treatments. The promoter-GUS (glucuronidase) activity analysis suggested that GmTIP2;3 was also expressed in the root, stem, and leaf, and preferentially expressed in the stele of root and stem, and the core promoter region was 1000 bp in length, located upstream of the ATG start codon. The GUS tissue and induced expression observations were consistent with the findings in soybean. In addition, subcellular localization showed that GmTIP2;3 was a plasma membrane-localized protein. Yeast heterologous expression revealed that GmTIP2;3 could improve tolerance to osmotic stress in yeast cells. Integrating these results, GmTIP2;3 might play an important role in response to osmotic stress in plants.

The nuclear protein GmbZIP110 has transcription activation activity and plays important roles in the response to salinity stress in soybean.

Plant basic-leucine zipper (bZIP) transcription factors play important roles in many biological processes and are involved in the regulation of salt stress tolerance. Previously, our lab generated digital gene expression profiling (DGEP) data to identify differentially expressed genes in a salt-tolerant genotype of Glycine soja (STGoGS) and a salt-sensitive genotype of Glycine max (SSGoGM). This DGEP data revealed that the expression (log2 ratio) of GmbZIP110 was up-regulated 2.76-fold and 3.38-fold in SSGoGM and STGoGS, respectively. In the present study, the salt inducible gene GmbZIP110 was cloned and characterized through phylogenetic analysis, subcellular localization and in silico transcript abundance analysis in different tissues. The functional role of this gene in salt tolerance was studied through transactivation analysis, DNA binding ability, expression in soybean composite seedlings and transgenic Arabidopsis, and the effect of GmbZIP110 on the expression of stress-related genes in transgenic Arabidopsis was investigated. We found that GmbZIP110 could bind to the ACGT motif, impact the expression of many stress-related genes and the accumulation of proline, Na+ and K+, and enhanced the salt tolerance of composite seedlings and transgenic Arabidopsis. Integrating all these results, we propose that GmbZIP110 plays a critical role in the response to salinity stress in soybean and has high potential usefulness in crop improvement.

Soybean C2H2-Type Zinc Finger Protein GmZFP3 with Conserved QALGGH Motif Negatively Regulates Drought Responses in Transgenic Arabidopsis

Plant response to environmental stresses is regulated by a complicated network of regulatory and functional genes. In this study, we isolated the putative stress-associated gene GmZFP3 (a C2H2-type Zinc finger protein gene) based on the previous finding that it was one of two genes located in the QTL region between the Satt590 and Satt567 markers related to soybean tolerance to drought. Temporal and spatial expression analysis using quantitative real-time PCR indicated that GmZFP3 was primarily expressed in roots, stems and leaf organs and was expressed at low levels in flowers and soybean pods. Moreover, GmZFP3 expression increased in response to polyethylene glycol (PEG) and Abscisic acid (ABA) treatments. In addition, subcellular localization analysis indicated that GmZFP3 was ubiquitously distributed in plant cells. Transgenic experiments indicated that GmZFP3 played a negative role in plant tolerance to drought. Analysis of ABA-related marker gene expression in Arabidopsis suggested that GmZFP3 might be involved in the ABA-dependent pathway during the drought stress response. Taken together, these results suggest that soybean GmZFP3 negatively regulates the drought response.

Over-expression of GmMYB39 leads to an inhibition of the isoflavonoid biosynthesis in soybean (Glycine max. L)

In this paper, we isolated and characterized a gene encoding the soybean MYB transcription factor, GmMYB39 (Accession No: XM_003538605). Analysis of the deduced amino acid sequence revealed that GmMYB39 contained N-terminal R2R3 repeats that corresponded to the DNA-binding domain of plant MYB-type proteins, which were highly conserved among the R2R3-MYB proteins. The detailed expression pattern of GmMYB39 in various tissues of soybean was investigated by quantitative RT-PCR. The transcript level was found to be higher in flowers than in other examined organs. In contrast, the GmMYB39 expression level was relatively weak in the pod. The GmMYB39–GFP fusion protein was found to localize in the nucleus of Arabidopsis mesophyll protoplasts. Over-expression of GmMYB39 in hairy roots resulted in a significant reduction of the transcript levels of PAL, C4H, CHS, 4CL, and CHR. Whereas, the IFS transcript level was slightly but not significantly increased, and no significant change in CHI expression was observed between over-expression and control roots. The repressing effect on expression of CHS was further supported by the results from co-transfection assays of CHS promoter (reporter) and GmMYB39 (effector) in soybean. Compared to the control (only with the reporter construct), a significant decrease in the GUS activity was observed in soybean hairy roots with both effector and reporter constructs. Furthermore, an ultimate decrease in isoflavonoids contents coincided with the decrease in the transcript levels of PAL, C4H, CHS, 4CL, and CHR. Overall, the results suggest that GmMYB39 plays an inhibiting role in regulating the isoflavonoid biosynthesis in soybean.

Strategies to Mitigate the Salt Stress Effects on Photosynthetic Apparatus and Productivity of Crop Plants

Soil salinization represents one of the major limiting factors of future increase in crop production through the expansion or maintaining of cultivation area in the future. High salt levels in soils or irrigation water represent major environmental concerns for agriculture in semiarid and arid zones. Recent advances in research provide great opportunities to develop effective strategies to improve crop salt tolerance and yield in different environments affected by the soil salinity. It was clearly demonstrated that plants employ both the common adaptative responses and the specific reactions to salt stress. The review of research results presented here may be helpful to understand the physiological, metabolic, developmental, and other reactions of crop plants to salinity, resulting in the decrease of biomass production and yield. In addition, the chapter provides an overview of modern studies on how to mitigate salt stress effects on photosynthetic apparatus and productivity of crop plants with the help of phytohormones, glycine betaine, proline, polyamines, paclobutrazol, trace elements, and nanoparticles. To understand well these effects and to discover new ways to improve productivity in salinity stress conditions, it is necessary to utilize efficiently possibilities of promising techniques and approaches focused on improvement of photosynthetic traits and photosynthetic capacity, which determines yield under salt stress conditions.

Genome-wide identification of Major Intrinsic Proteins in Glycine soja and characterization of GmTIP2;1 function under salt and water stress

In different plant species, aquaporins (AQPs) facilitate water movement by regulating root hydraulic conductivity under diverse stress conditions such as salt and water stresses. To improve survival and yield of crop plants, a detailed understanding of stress responses is imperative and required. We used Glycine soja genome as a tool to study AQPs, considering it shows abundant genetic diversity and higher salt environment tolerance features and identified 62 GsAQP genes. Additionally, this study identifies major aquaporins responsive to salt and drought stresses in soybean and elucidates their mode of action through yeast two-hybrid assay and BiFC. Under stress condition, the expression analysis of AQPs in roots and leaves of two contrasting ecotypes of soybean revealed diverse expression patterns suggesting complex regulation at transcriptional level. Based on expression analysis, we identify GmTIP2;1 as a potential candidate involved in salinity and drought responses. The overexpression of GmTIP2;1 in Saccharomyces cerevisiae as well as in-planta enhanced salt and drought tolerance. We identified that GmTIP2;1 forms homodimers as well as interacts with GmTIP1;7 and GmTIP1;8. This study augments our knowledge of stress responsive pathways and also establishes GmTIP2;1 as a new stress responsive gene in imparting salt stress tolerance in soybean.

Genome-wide characterization of the ankyrin repeats gene family under salt stress in soybean

Ankyrin repeats (ANK) gene family are common in diverse organisms and play important roles in cell growth, development and response to environmental stresses. Recently, genome-wide identification and evolutionary analyses of the ANK gene family have been carried out in Arabidopsis, rice and maize. However, little is known about the ANK genes in the whole soybean genome. In this study, we described the identification and structural characterization of 162ANK genes in soybean (GmANK). Then, comprehensive bioinformatics analyses of GmANK genes family were performed including gene locus, phylogenetic, domain composition analysis, chromosomal localization and expression profiling. Domain composition analyses showed that GmANK proteins formed eleven subfamilies in soybean. In sicilo expression analysis of these GmANK genes demonstrated that GmANK genes show a diverse/various expression pattern, suggesting that functional diversification of GmANK genes family. Based on digital gene expression profile (DGEP) data between cultivated soybean and wild type under salt treatment, some GmANKs related to salt/drought response were investigated. Moreover, the expression pattern and subcellular localization of GmANK6 were performed. The results will provide important clues to explore ANK genes expression and function in future studies in soybean.

Comparative expression analysis of Calcineurin B-like family gene CBL10A between salt-tolerant and salt-sensitive cultivars in B. oleracea

Calcineurin B-like proteins (CBLs) are plant calcium sensors that play a critical role in the regulation of plant growth and response to stress. Many CBLs have been identified in the calcium signaling pathway in both Arabidopsis and rice. However, information about BoCBLs genes from Brassica oleracea has not been reported. In the present study, we identified 13 candidate CBL genes in the B. oleracea genome based on the conserved domain of the Calcineurin B-like family, and we carried out a phylogenetic analysis of CBLs among Arabidopsis, rice, maize, cabbage and B. oleracea. For B. oleracea, the distribution of the predicted BoCBL genes was uneven among the five chromosomes. Sequence analysis showed that the nucleotide sequences and corresponding protein structure of BoCBLs were highly conserved, i.e., all of the putative BoCBLs contained 6-8 introns, and most of the exons of those genes contained the same number of nucleotides and had high sequence identities. All BoCBLs consisted of four EF-Hand functional domains, and the distance between the EF-hand motifs was conserved. Evolutionary analysis revealed that the CBLs were classified into two subgroups. Additionally, the CBL10A gene was cloned from salt-tolerant (CB6) and salt-sensitive (CB3) cultivars using RT-PCR. The results indicated that the cloned gene had a substantial difference in length (741bp in CB3 and 829bp in CB6) between these two cultivars. The deduced CBL10A protein in CB6 had four EF-hand structural domains, which have an irreplaceable role in calcium-binding and have calcineurin A subunit binding sites, while the BoCBL10A protein in CB3 had only two EF-hand structural domains and lacked calcineurin A subunit binding sites. The expression level of the BoCBL10A gene between salt tolerance (CB6)and sensitive varieties(CB3) under salt stress was significantly different (P<0.01 and P<0.05). The expression of BoCBL10A gene was relatively higher in salt-tolerant (CB6) cultivar under salt stress, with a longer period of up-regulation expression and a shorter time responding to salt, compared with the salt-sensitive (CB3) cultivar. We speculate that these differences in the coding region of BoCBL10A may lead to the different salt responses between these two cultivars.