Investigation of morpho-physiolgical traits and gene expression in barley under nitrogen deficiency.

Nitrogen (N) is an essential element for plant growth, and its deficiency influences plants at several physiological and gene expression levels. Barley (Hordeum vulgare) is one of the most important food grains from the Poaceae family and one of the most important staple food crops. However, the seed yield is limited by a number of stresses, the most important of which is the insufficient use of N. Thus, there is a need to develop N-use effective cultivars. In this study, comparative physiological and molecular analyses were performed using leaf and root tissues from 10 locally grown barley cultivars. The expression levels of nitrate transporters, HvNRT2 genes, were analyzed in the leaf and root tissues of N-deficient (ND) treatments of barley cultivars after 7 and 14 days following ND treatment as compared to the normal condition. Based on the correlation between the traits, root length (RL) had a positive and highly significant correlation with fresh leaf weight (FLW) and ascorbate peroxidase (APX) concentration in roots, indicating a direct root and leaf relationship with the plant development under ND. From the physiological aspects, ND enhanced carotenoids, chlorophylls a/b (Chla/b), total chlorophyll (TCH), leaf antioxidant enzymes such as ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT), and root antioxidant enzymes (APX and POD) in the Sahra cultivar. The expression levels of HvNRT2.1, HvNRT2.2, and HvNRT2.4 genes were up-regulated under ND conditions. For the morphological traits, ND maintained root dry weight among the cultivars, except for Sahra. Among the studied cultivars, Sahra responded well to ND stress, making it a suitable candidate for barely improvement programs. These findings may help to better understand the mechanism of ND tolerance and thus lead to the development of cultivars with improved nitrogen use efficiency (NUE) in barley.

Differential expression of the genes encoding immune system components in response to Pseudomonas syringae and Pseudomonas aeruginosa in Arabidopsis thaliana.

In innate immunity, the first layer of defense against any microbial infection is triggered by the perception of pathogen-associated molecular patterns by highly specific pattern recognition receptors. The Pseudomonas syringae pv. tomato and Pseudomonas aeruginosa are plant-pathogenic bacterial species that include pathogenic strains in a wide range of different plant species. In the current study, extensive analysis including gene expression of 12 hub genes, gene ontology, protein-protein interaction, and cis-element prediction to dissect the Arabidopsis response to above-mentioned bacteria were performed. Further, we evaluated weighted co-expression network analysis (WGCNA) in the wild-type plants and coi-1 mutant line and determined changes in responsive genes at two time-points (4 and 8 h) of post-treatment with P. syringae and P. aeruginosa. Compared to the wild-type plants, coi-1 mutant showed significant expression in most of the genes involved, indicating that their protein products have important role in innate immunity and RNA silencing pathways. Our findings showed that 12 hub genes were co-expressed in response to P. syringae and P. aeruginosa infections. Based on the network analysis, transcription factors, receptors, protein kinase, and pathogenesis-related protein (PR1) were involved in the immunity system. Gene ontology related to each module was involved in defense response, protein serine kinase activity, and primary miRNA processing. Based on the cis-elements prediction, MYB, MYC, WRE3, W-box, STRE, and ARE contained the most number of cis-elements in co-expressed network genes. Also, in coi-1 mutant, most responsive genes against theses pathogens were up-regulated. The knowledge gained in the gene expression analysis in response to P. syringae and P. aeruginosa in the model plant, i.e., Arabidopsis, is essential to allow us to gain more insight about the innate immunity in other crops.

Comparative analysis of physiological traits and gene expression patterns in nitrogen deficiency among barley cultivars.

BACKGROUND: Nitrogen is one of the most important mineral nutrients for plants and is absorbed by the root system mainly in the inorganic form (NH+4 and NO-3). Plants absorb nitrogen as a food source for growth, biomass production, and development. Nitrogen is mainly absorbed as nitrate, which is the most common source of nitrogen available to higher plants. One of the unique features of nitrate transport is that NO-3 is both a substrate for transport and an inducer of NO-3 transport systems in genes and at physiological levels. METHODS: In the present study, morphological and physiological traits (chlorophyll a/b, total chlorophyll, and carotenoid, antioxidant enzymes, and protein content), correlation between traits and gene expression, and principle component analysis of traits among five barley cultivars were measured in response to nitrogen deficiency (ND). The starved plants were transferred to a nutrient solution containing 0.2 mM and 2 mM NO-3 up to 7 and 14 days after ND application and non-stressed conditions, respectively. RESULTS: Gene expression analysis revealed that the 10 HvNRT2 genes were induced in the leaf and root tissues at 7 and 14 days after ND treatments in five barley cultivars. Expression of NRT2 genes by relative quantitative qRT-PCR analysis for 10 HvNRT2 genes were determined. Based on the gene expression, HvNRT2.1, HvNRT2.2, and HvNRT2.4 were strongly induced by NO-3, peaking at 7 and 14 days after ND treatment. In contrast, the HvNRT2.4 showed only moderate induction in both leaves and roots. From our results, the Reyhan cultivar showed a significant increase in root fresh weight (RFW), protein content, and antioxidant enzyme activity in roots at 7 and 14 days after ND treatment as compared to the non-stressed condition. A highly positive correlation was observed between root catalase (CATr) and HvNRT2.2/2.5/2.6 leaves. CONCLUSION: The expression of HvNRT2.4 is increased during long-term nitrogen starvation, while the expression of HvNRT2.1 and HvNRT2.2 are transiently increased by ND. Based on physiological and morphological traits and molecular mechanisms, the Reyhan is considered a tolerant cultivar under ND condition.

Identification of myosin genes and their expression in response to biotic (PVY, PVX, PVS, and PVA) and abiotic (Drought, Heat, Cold, and High-light) stress conditions in potato.

BACKGROUND: Plant organelles are highly motile where their movement is significant for fast distribution of material around the cell, facilitation of the plant's ability to respond to abiotic and biotic signals, and for appropriate growth. Abiotic and biotic stresses are among the major factors limiting crop yields, and biological membranes are the first target of these stresses. Plants utilize adaptive mechanisms namely myosin to repair injured membranes following exposure to abiotic and biotic stresses. OBJECTIVE: Due to the economic importance and cultivation of potato grown under abiotic and biotic stress prone areas, identification and characterization of myosin family members in potato were performed in the present research. METHODS: To identify the myosin genes in potato, we performed genome-wide analysis of myosin genes in the S. tuberosum genome using the phytozome. All putative sequences were approved with the interproscan. Bioinformatics analysis was conducted using phylogenetic tree, gene structure, cis-regulatory elements, protein-protein interaction, and gene expression. RESULT: The majority of the cell machinery contain actin cytoskeleton and myosins, where motility of organelles are dependent on them. Homology-based analysis was applied to determine seven myosin genes in the potato genome. The members of myosin could be categorized into two groups (XI and VIII). Some of myosin proteins were sub-cellularly located in the nucleus containing 71.5% of myosin proteins and other myosin proteins were localized in the mitochondria, plasma-membrane, and cytoplasm. Determination of co-expressed network, promoter analysis, and gene structure were also performed and gene expression pattern of each gene was surveyed. Number of introns in the gene family members varied from 1 to 39. Gene expression analysis demonstrated that StMyoXI-B and StMyoVIII-2 had the highest transcripts, induced by biotic and abiotic stresses in all three tissues of stem, root, and leaves, respectively. Overall, different cis-elements including abiotic and biotic responsive, hormonal responsive, light responsive, defense responsive elements were found in the myosin promoter sequences. Among the cis-elements, the MYB, G-box, ABRE, JA, and SA contributed the most in the plant growth and development, and in response to abiotic and biotic stress conditions. CONCLUSION: Our results showed that myosin genes can be utilized in breeding programs and genetic engineering of plants with the aim of increasing tolerance to abiotic and biotic stresses, especially to viral stresses such as PVY, PVX, PVA, PVS, high light, drought, cold and heat.

Genome-wide identification of 14-3-3 gene family and characterization of their expression in developmental stages of Solanum tuberosum under multiple biotic and abiotic stress conditions.

GF14 proteins are a family of conserved proteins involved in many cellular processes including transport, growth, metabolism, and stress response. However, only few reports are available regarding the 14-3-3 genes in potato. In this study, twelve 14-3-3 genes were detected in the potato genome. Based on their phylogenetic relationships, the StGF14 family members were categorized into two classes. Gene expression analysis demonstrated that StGF14h, StGF14a, and StGF14k had the highest gene expression, induced by abiotic and biotic stresses in all three tissues. The number of exons in 14-3-3 genes ranged from four to seven and most of these genes in the same subfamily had similar exon-intron patterns. The results of our study showed that the conserved motifs are similar in most of the proteins in each group. The intron-exon patterns and the composition of conserved motifs validated the 14-3-3 gene phylogenetic classification. According to the genome distribution results, 14-3-3 genes were located unevenly on the 12 Solanum tuberosum chromosomes. We find out 97 orthologous gene pairs between potato and Arabidopsis as well as 15 paralogous genes among potato genomes. Our results showed that GF-14 genes have an effective role in functional and molecular mechanisms in response to environmental stresses.

Senescence-associated proteins and nitrogen remobilization in grain filling under drought stress condition.

BACKGROUND: Plants use escape strategies including premature senescence and leaf reduction to cope in response to drought stress, which in turn reduces plant leaves and photosynthesis. This strategy allows the new generation (seeds) to survive under drought but, plants experience more yield loss during stress condition. The amount of damage caused by drought stress is compensated by the expression of genes involved in regulating leaf aging. Leaf senescence alters the expression of thousands of genes and ultimately affecting grain protein content, grain yield, and nitrogen utilization efficiency. Also, under drought stress, nitrogen in the soil will not become as much available and causes the beginning and acceleration of the senescence process of leaves. This review identified proteins signaling and functional proteins involved in senescence. Further, transcription factors and cell wall degradation enzymes (proteases) related to senescence during drought stress were surveyed. We discuss the regulatory pathways of genes as a result of the degradation of proteins during senescence process. Senescence is strongly influenced by plant hormones and environmental factors including the availability of nitrogen. During maturity or drought stress, reduced nitrogen uptake can cause nitrogen to be remobilized from leaves and stems to seeds, eventually leading to leaf senescence. Under these conditions, genes involved in chloroplast degradation and proteases show increased expression. The functional (proteases) and regulatory proteins such as protein kinases and phosphatases as well as transcription factors (AP2/ERF, NAC, WRKY, MYB, and bZIP) are involved in leaf senescence and drought stress. SHORT CONCLUSION: In this review, senescence-associated proteins involved in leaf senescence and regulatory and functional proteins in response to drought stress during grain filling were surveyed. The present study predicts on the role of nitrogen transporters, transcription factors and regulatory genes involved in the late stages of plant growth with the aim of understanding their mechanisms of action during grain filling stage. For a better understanding, the relevant evidence for the balance between grain filling and protein breakdown during grain filling in cereals is presented.

Characterization of genetic diversity in chickpea using SSR markers, Start Codon Targeted Polymorphism (SCoT) and Conserved DNA-Derived Polymorphism (CDDP).

To evaluate the genetic diversity among 48 genotypes of chickpea comprising cultivars, landraces and internationally developed improved lines genetic distances were evaluated using three different molecular marker techniques: Simple Sequence Repeat (SSR); Start Codon Targeted (SCoT) and Conserved DNA-derived Polymorphism (CDDP). Average polymorphism information content (PIC) for SSR, SCoT and CDDP markers was 0.47, 0.45 and 0.45, respectively, and this revealed that three different marker types were equal for the assessment of diversity amongst genotypes. Cluster analysis for SSR and SCoT divided the genotypes in to three distinct clusters and using CDDP markers data, genotypes grouped in to five clusters. There were positive significant correlation (r = 0.43, P < 0.01) between similarity matrix obtained by SCoT and CDDP. Three different marker techniques showed relatively same pattern of diversity across genotypes and using each marker technique it's obvious that diversity pattern and polymorphism for varieties were higher than that of genotypes, and CDDP had superiority over SCoT and SSR markers. These results suggest that efficiency of SSR, SCOT and CDDP markers was relatively the same in fingerprinting of chickpea genotypes. To our knowledge, this is the first detailed report of using targeted DNA region molecular marker (CDDP) for genetic diversity analysis in chickpea in comparison with SCoT and SSR markers. Overall, our results are able to prove the suitability of SCoT and CDDP markers for genetic diversity analysis in chickpea for their high rates of polymorphism and their potential for genome diversity and germplasm conservation.