Isolation and expression studies of the ERD15 gene involved in drought-stressed responses

Sweet Potato as a Key Crop for Food Security under the Conditions of Global Climate Change: A Review

Sweet potato is one of the most economically important crops for addressing global food security and climate change issues, especially under conditions of extensive agriculture, such as those found in developing countries. However, osmotic stress negatively impacts the agronomic and economic productivity of sweet potato cultivation by inducing several morphological, physiological, and biochemical changes. Plants employ many signaling pathways to respond to water stress by modifying their growth patterns, activating antioxidants, accumulating suitable solutes and chaperones, and making stress proteins. These physiological, metabolic, and genetic modifications can be employed as the best indicators for choosing drought-tolerant genotypes. The main objective of sweet potato breeding in many regions of the world, especially those affected by drought, is to obtain varieties that combine drought tolerance with high yields. In this regard, the study of the physiological and biochemical features of certain varieties is important for the implementation of drought resistance measures. Adapted genotypes can be selected and improved for particular growing conditions by using suitable tools and drought tolerance-related selection criteria. By regulating genetics in this way, the creation of drought-resistant varieties may become cost-effective for smallholder farmers. This review focuses on the drought tolerance mechanisms of sweet potato, the effects of drought stress on its productivity, its crop management strategies for drought mitigation, traditional and molecular sweet potato breeding methods for drought tolerance, and the use of biotechnological methods to increase the tolerance of sweet potato to drought.

Morphologically and genetically diverse forage pea (Pisum sativum var. arvense L.) genotypes under single and combined salt and drought stresses

Salinity and drought stresses limit agricultural productivity of many crops including forage pea which is an important forage legume. Due to increasing importance of legumes in forage production, there is a clear need to investigate the underlying affects of salinity and drought stresses on forage pea. This study was designed to understand how single or combined salinity and drought stresses impact on physio-biochemical and molecular status of morphologically and genetically diverse forage pea genotypes. Firstly, yield-related parameters were determined under three-year field experiment. The results revealed that the agro-morphological features of the genotypes are significantly different. Afterwards, the sensitivities of the 48 forage pea genotypes were determined against single and combined salinity and drought stresses by performing growth parameters, biochemical status, antioxidative enzymes, and endogenous hormones. Also, the salt and drought-related gene expressions were evaluated under normal and stressed conditions. The results collectively showed that the genotypes of O14, and T8 were more tolerant against combined stress compared to others, via activating antioxidative enzymes (CAT, GR, and SOD), endogenous hormones (IAA, ABA, and JA), stress-related genes (DREB3, DREB5, bZIP11, bZIP37, MYB48, ERD, RD22) and leaf senescence genes (SAG102, SAG102). These genotypes could be used to develop pea plants that tolerate salinity or drought stress conditions. To the best of our knowledge, the present study is the first detailed study in pea against combined salt and drought stresses.

Genome-Wide Characterization and Function Analysis of ZmERD15 Genes' Response to Saline Stress in Zea mays L

Early responsive dehydration (ERD) genes can be rapidly induced by dehydration. ERD15 genes have been confirmed to regulate various stress responses in plants. However, the maize ERD15 members have not been characterized. In the present study, a total of five ZmERD15 genes were identified from the maize genome and named ZmERD15a, ZmERD15b, ZmERD15c, ZmERD15d, and ZmERD15e. Subsequently, their protein properties, gene structure and duplication, chromosomal location, cis-acting elements, subcellular localization, expression pattern, and over-expression in yeast were analyzed. The results showed that the ZmERD15 proteins were characterized by a similar size (113-159 aa) and contained a common domain structure, with PAM2 and adjacent PAE1 motifs followed by an acidic region. The ZmERD15 proteins exhibited a close phylogenetic relationship with OsERD15s from rice. Five ZmERD15 genes were distributed on maize chromosomes 2, 6, 7, and 9 and showed a different exon-intron organization and were expanded by duplication. Besides, the promoter region of the ZmERD15s contained abundant cis-acting elements that are known to be responsive to stress and hormones. Subcellular localization showed that ZmERD15b and ZmERD15c were localized in the nucleus. ZmERD15a and ZmERD15e were localized in the nucleus and cytoplasm. ZmERD15d was localized in the nucleus and cell membrane. The results of the quantitative real-time PCR (qRT-PCR) showed that the expression of the ZmERD15 genes was regulated by PEG, salinity, and ABA. The heterologous expression of ZmERD15a, ZmERD15b, ZmERD15c, and ZmERD15d significantly enhanced salt tolerance in yeast. In summary, a comprehensive analysis of ZmERD15s was conducted in the study. The results will provide insights into further dissecting the biological function and molecular mechanism of ZmERD15s regulating of the stress response in maize.

Ocimum metabolomics in response to abiotic stresses: Cold, flood, drought and salinity

Ocimum tenuiflorum is a widely used medicinal plant since ancient times and still continues to be irreplaceable due to its properties. The plant has been explored chemically and pharmacologically, however, the molecular studies have been started lately. In an attempt to get a comprehensive overview of the abiotic stress response in O. tenuiflorum, de novo transcriptome sequencing of plant leaves under the cold, drought, flood and salinity stresses was carried out. A comparative differential gene expression (DGE) study was carried out between the common transcripts in each stress with respect to the control. KEGG pathway analysis and gene ontology (GO) enrichment studies exhibited several modifications in metabolic pathways as the result of four abiotic stresses. Besides this, a comparative metabolite profiling of stress and control samples was performed. Among the cold, drought, flood and salinity stresses, the plant was most susceptible to the cold stress. Severe treatments of all these abiotic stresses also decreased eugenol which is the main secondary metabolite present in the O. tenuiflorum plant. This investigation presents a comprehensive analysis of the abiotic stress effects in O. tenuiflorum. Current study provides an insight to the status of pathway genes’ expression that help synthesizing economically valuable phenylpropanoids and terpenoids related to the adaptation of the plant. This study identified several putative abiotic stress tolerant genes which can be utilized to either breed stress tolerant O. tenuiflorum through pyramiding or generating transgenic plants.

VaERD15, a Transcription Factor Gene Associated with Cold-Tolerance in Chinese Wild Vitis amurensis

Early responsive to dehydration (ERD) genes can be rapidly induced to counteract abiotic stresses, such as drought, low temperatures or high salinities. Here, we report on an ERD gene (VaERD15) related to cold tolerance from Chinese wild Vitis amurensis accession 'Heilongjiang seedling'. The full-length VaERD15 cDNA is 685 bp, including a 66 bp 5'-untranslated region (UTR), a 196 bp 3'-UTR region and a 423 bp open reading frame encoding 140 amino acids. The VaERD15 protein shares a high amino acid sequence similarity with ERD15 of Arabidopsis thaliana. In our study, VaERD15 was shown to have a nucleic localization function and a transcriptional activation function. Semi-quantitative PCR and Western blot analyses showed that VaERD15 was constitutively expressed in young leaves, stems and roots of V. amurensis accession 'Heilongjiang seedling' plants, and expression levels increased after low-temperature treatment. We also generated a transgenic Arabidopsis Col-0 line that over-expressed VaERD15 and carried out a cold-treatment assay. Real-time quantitative PCR (qRT-PCR) and Western blot analyses showed that as the duration of cold treatment increased, the expression of both gene and protein levels increased continuously in the transgenic plants, while almost no expression was detected in the wild type Arabidopsis. Moreover, the plants that over-expressed VaERD15 showed higher cold tolerance and accumulation of proline, soluble sugars, proteins, malondialdehyde and three antioxidases (superoxide dismutase, peroxidase, and catalase). Lower levels of relative ion leakage also occurred under cold stress. Taken together, our results indicate that the transcription factor VaERD15 was induced by cold stress and was able to enhance cold tolerance.

Transcription activation activity of ERD15 protein from Morus indica

Early Responsive to Dehydration (ERD) genes are described as rapid response mediators of dehydration stress. Recently, ERD15 has emerged as a novel stress induced transcription factor which might be involved in mediating distinct stress responses in plants. In order to determine whether mulberry ERD15 can act as functional transcription factor, yeast-based assays were performed. Mulberry ERD15 was found to drive high level reporter gene expression in yeast which suggests it may function as a transcription factor. However, due to lack of an identifiable DNA binding domain, deletion analysis was carried out to determine the putative region of the protein involved in mediating protein-DNA interaction. Our results indicate that the region between 70 and 100 amino acids is critical in conferring transcription activation activity and might harbor the DNA binding region of ERD15.

Epiallelic changes in known stress-responsive genes under extreme drought conditions in Brassica juncea (L.) Czern

Under severe drought conditions, Brassica juncea shows differential methylation and demethylation events, such that certain epialleles are silenced and some are activated. The plant employed avoidance strategy by delaying apoptosis through the activation of several genes. Harsh environmental conditions pose serious threat to normal growth and development of crops, sometimes leading to their death. However, plants have developed an essential mechanism of modulation of gene activities by epigenetic modifications. Brassica juncea is an important oilseed crop contributing effectively to the economy of India. In the present investigation, we studied the changes in the methylation level of various stress-responsive genes of B. juncea variety RH30 by methylation-dependent immune-precipitation-chip in response to severe drought. On the basis of changes in the number of differential methylation regions in response to drought, the promoter regions were designated as hypermethylated and hypomethylated. Gene body methylation increased in all the genes, whereas promoter methylation was dependent on the function of the gene. Overall, the genes responsible for delaying apoptosis were hypomethylated and many genes responsible for normal routine activities were hypermethylated at promoter regions, thereby suggesting that these may be suspending the activities under harsh conditions.