Ethanol-Mediated Novel Survival Strategy against Drought Stress in Plants.

Water scarcity is a serious agricultural problem causing significant losses to crop yield and product quality. The development of technologies to mitigate the damage caused by drought stress is essential for ensuring a sustainable food supply for the increasing global population. We herein report that the exogenous application of ethanol, an inexpensive and environmentally friendly chemical, significantly enhances drought tolerance in Arabidopsis thaliana, rice and wheat. The transcriptomic analyses of ethanol-treated plants revealed the upregulation of genes related to sucrose and starch metabolism, phenylpropanoids and glucosinolate biosynthesis, while metabolomic analysis showed an increased accumulation of sugars, glucosinolates and drought-tolerance-related amino acids. The phenotyping analysis indicated that drought-induced water loss was delayed in the ethanol-treated plants. Furthermore, ethanol treatment induced stomatal closure, resulting in decreased transpiration rate and increased leaf water contents under drought stress conditions. The ethanol treatment did not enhance drought tolerance in the mutant of ABI1, a negative regulator of abscisic acid (ABA) signaling in Arabidopsis, indicating that ABA signaling contributes to ethanol-mediated drought tolerance. The nuclear magnetic resonance analysis using 13C-labeled ethanol indicated that gluconeogenesis is involved in the accumulation of sugars. The ethanol treatment did not enhance the drought tolerance in the aldehyde dehydrogenase (aldh) triple mutant (aldh2b4/aldh2b7/aldh2c4). These results show that ABA signaling and acetic acid biosynthesis are involved in ethanol-mediated drought tolerance and that chemical priming through ethanol application regulates sugar accumulation and gluconeogenesis, leading to enhanced drought tolerance and sustained plant growth. These findings highlight a new survival strategy for increasing crop production under water-limited conditions.

Overexpression of nicotinamidase 3 (NIC3) gene and the exogenous application of nicotinic acid (NA) enhance drought tolerance and increase biomass in Arabidopsis.

KEY MESSAGE: Overexpressing Nicotinamidase 3 gene, and the exogenous application of its metabolite nicotinic acid (NA), enhance drought stress tolerance and increase biomass in Arabidopsis thaliana. With progressive global climatic changes, plant productivity is threatened severely by drought stress. Deciphering the molecular mechanisms regarding genes responsible for balancing plant growth and stress amelioration could imply multiple possibilities for future sustainable goals. Nicotinamide adenine dinucleotide (NAD) biosynthesis and recycling/ distribution is a crucial feature for plant growth. The current study focuses on the functional characterization of nicotinamidase 3 (NIC3) gene, which is involved in the biochemical conversion of nicotinamide (NAM) to nicotinic acid (NA) in the salvage pathway of NAD biosynthesis. Our data show that overexpression of NIC3 gene enhances drought stress tolerance and increases plant growth. NIC3-OX plants accumulated more NA as compared to WT plants. Moreover, the upregulation of several genes related to plant growth/stress tolerance indicates that regulating the NAD salvage pathway could significantly enhance plant growth and drought stress tolerance. The exogenous application of nicotinic acid (NA) showed a similar phenotype as the effect of overexpressing NIC3 gene. In short, we contemplated the role of NIC3 gene and NA application in drought stress tolerance and plant growth. Our results would be helpful in engineering plants with enhanced drought stress tolerance and increased growth potential.

Roles of subcellular metal homeostasis in crop improvement.

Improvement of crop production in response to rapidly changing environmental conditions is a serious challenge facing plant breeders and biotechnologists. Iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) are essential micronutrients for plant growth and reproduction. These minerals are critical to several cellular processes including metabolism, photosynthesis, and cellular respiration. Regulating the uptake and distribution of these minerals could significantly improve plant growth and development, ultimately leading to increased crop production. Plant growth is limited by mineral deficiency, but on the other hand, excess Fe, Mn, Cu, and Zn can be toxic to plants; therefore, their uptake and distribution must be strictly regulated. Moreover, the distribution of these metals among subcellular organelles is extremely important for maintaining optimal cellular metabolism. Understanding the mechanisms controlling subcellular metal distribution and availability would enable development of crop plants that are better adapted to challenging and rapidly changing environmental conditions. Here, we describe advances in understanding of subcellular metal homeostasis, with a particular emphasis on cellular Fe homeostasis in Arabidopsis and rice, and discuss strategies for regulating cellular metabolism to improve plant production.

Identification and validation of superior housekeeping gene(s) for qRT-PCR data normalization in Agave sisalana (a CAM-plant) under abiotic stresses.

The adaptive mechanisms in Agave species enable them to survive and exhibit remarkable tolerance to abiotic stresses. Quantitative real-time PCR is a highly reliable approach for validation of targeted differential gene expression. However, stable housekeeping gene(s) is prerequisite for accurate normalization of expression data by qRT-PCR. Till date, no systematic validation study for candidate housekeeping gene identification or evaluation has been carried-out in Agave species. A total of 17 candidate housekeeping genes were identified from the de novo assembled transcriptomic data of A. sisalana and rigorously analyzed for expression stability assessment under drought, heat, cold and NaCl stress. Different statistical algorithms like geNorm, BestKeeper, NormFinder, and RefFinder on expression data determined the superior housekeeping gene(s) for accurate normalization of the gene of interest (GOI). The comprehensive evaluation revealed the ß-Tub 4, WIN-1 and CYC-A as the most stable, while EEF1α, GAPDH, and UBE2 were ranked as the least stable genes in pooled samples. Pairwise combination by geNorm showed that up to two housekeeping genes would be adequate to normalize the GOI expression data precisely. Validation of identified most and least stable housekeeping genes was carried-out by normalizing the expression data of AsHSP20 under abiotic stress conditions. Copy number of AsHSP20 gene supports the reliability of the genes used for normalization. This is the first report on the screening and validation of the housekeeping genes under abiotic stress condition in A. sisalana that would assist to understand the stress tolerance mechanisms by novel gene identification and accurate validation.

Modification of miRNA Expression through plant extracts and compounds against breast cancer: Mechanism and translational significance.

BACKGROUND: Cancer is hyper-proliferative, multi-factorial and multi-step, heterogeneous group of molecular disorders. It is the second most reported disease after heart diseases. Breast carcinoma is the foremost death causing disease in female population worldwide. Cancer can be controlled by regulating the gene expression. Current therapeutic options are associated with severe side effects and are expensive for the people living in under-developed countries. Plant derived substances have potential application against different diseases like cancer, inflammation and viral infections. HYPOTHESIS: The mechanism of action of the medicinal plants is largely unknown. Targeting gene network and miRNA using medicinal plants could help in improving the therapeutic options against cancer. METHODS: The literature from 135 articles was reviewed by using PubMed, google scholar, Science direct to find out the plants and plant-based compounds against breast cancer and also the studies reporting their mechanistic route of action both at coding and noncoding RNA levels. RESULTS: Natural products act as selective inhibitors of the cancerous cells by targeting oncogenes and tumor suppressor genes or altering miRNA expression. Natural compounds like EGCG from tea, Genistein from fava beans, curcumin from turmeric, DIM found in cruciferous, Resveratrol a polyphenol and Quercetin a flavonoid is found in various plants have been studied for their anticancer activity. The EGCG was found to inhibit proliferative activity by modulating miR-16 and miR-21. Similarly, DIM was found to down regulate miR-92a which results to modulate NFkB and stops cancer development. Another plant-based compound Glyceollins found to upregulate miR-181c and miR-181d having role in tumor suppression. It also found to regulate miR-22, 29b and c, miR-30d, 34a and 195. Quercetin having anti-cancer activity induce the apoptosis through regulating miR-16, 26b, 34a, let-7g, 125a and miR-605 and reduce the miRNA expression like miR-146a/b, 503 and 194 which are involved in metastasis. CONCLUSION: Targeting miRNA expression using natural plant extracts can have a reverse effect on cell proliferation; turning on and off tumor-inducing and suppressing genes. It can be efficiently adopted as an adjuvant with the conventional form of therapies to increase their efficacy against cancer progression.

De novo assembly of Agave sisalana transcriptome in response to drought stress provides insight into the tolerance mechanisms.

Agave, monocotyledonous succulent plants, is endemic to arid regions of North America, exhibiting exceptional tolerance to their xeric environments. They employ various strategies to overcome environmental constraints, such as crassulacean acid metabolism, wax depositions, and protective leaf morphology. Genomic resources of Agave species have received little attention irrespective of their cultural, economic and ecological importance, which so far prevented the understanding of the molecular bases underlying their adaptations to the arid environment. In this study, we aimed to elucidate molecular mechanism(s) using transcriptome sequencing of A. sisalana. A de novo approach was applied to assemble paired-end reads. The expression study unveiled 3,095 differentially expressed unigenes between well-irrigated and drought-stressed leaf samples. Gene ontology and KEGG analysis specified a significant number of abiotic stress responsive genes and pathways involved in processes like hormonal responses, antioxidant activity, response to stress stimuli, wax biosynthesis, and ROS metabolism. We also identified transcripts belonging to several families harboring important drought-responsive genes. Our study provides the first insight into the genomic structure of A. sisalana underlying adaptations to drought stress, thus providing diverse genetic resources for drought tolerance breeding research.

Identification and Characterization of the Diverse Stress-Responsive R2R3-RMYB Transcription Factor from Hibiscus sabdariffa L.

Various regulatory proteins play a fundamental role to manage the healthy plant growth under stress conditions. Differential display reverse transcriptase PCR and random amplification of cDNA ends (RACE) was used to explore the osmotic stress-responsive transcripts. We identified and characterized the salt stress-responsive R2R3 type RMYB transcription factor from Hibiscus sabdariffa which has an open reading frame of 690 bp, encoding 229 long chain amino acids. In silico analysis confirmed the conserved R2 and R3 domain as well as an NLS-1 localization site. The deduced amino acids of RMYB shared 83, 81, 80, 79, 72, 71, and 66% homology with Arabidopsis thaliana, Glycine max, Oryza sativa, Zea maize, Malus domestica, Populus tremula × Populus alba, and Medicago sativa specific MYB family, respectively. We observed the gene upregulation in stem, leaf, and root tissue in response to abiotic stress. Furthermore, RMYB gene was cloned into plant expression vector under CaMV35S promoter and transformed to Gossypium hirsutum: a local cotton cultivar. Overexpression of RMYB was observed in transgenic plants under abiotic stresses which further suggests its regulatory role in response to stressful conditions. The RMYB transcription factor-overexpressing in transgenic cotton plants may be used as potential agent for the development of stress tolerant crop cultivars.

Microarray: gateway to unravel the mystery of abiotic stresses in plants.

Environmental factors, such as drought, salinity, extreme temperature, ozone poisoning, metal toxicity etc., significantly affect crops. To study these factors and to design a possible remedy, biological experimental data concerning these crops requires the quantification of gene expression and comparative analyses at high throughput level. Development of microarrays is the platform to study the differential expression profiling of the targeted genes. This technology can be applied to gene expression studies, ranging from individual genes to whole genome level. It is now possible to perform the quantification of the differential expression of genes on a glass slide in a single experiment. This review documents recently published reports on the use of microarrays for the identification of genes in different plant species playing their role in different cellular networks under abiotic stresses. The regulation pattern of differentially-expressed genes, individually or in group form, may help us to study different pathways and functions at the cellular and molecular level. These studies can provide us with a lot of useful information to unravel the mystery of abiotic stresses in important crop plants.