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Transcriptional profiling in Finger millet (Eleusine coracana) genotypes provides insights into the molecular basis of salinity tolerance in tolerant genotype.

ABSTRACT: In present study we compared transcriptional response to salinity stress between susceptible CO 12 and tolerant genotype trichy 1 of finger millet. We found out that several functional group of genes like transporters, transcription factors, genes involved in cell signalling, osmotic homeostasis, compatible solutes biosynthesis were upregulated more in tolerant genotype as compared to susceptible genotype in response to salinity stress. Salnity inhibited photosynthetic capacity and photosynthesis related genes more in susceptible genotype as compared to tolerant genotype. Identified genes are excellent targets for further functional studies in order to understand more specific molecular mechanisms of salt tolerance in two genotypes of finger millet and can be further used for developing salinity tolerant crops through genetic engineering.

ORGANISM(S): Eleusine coracana

PROVIDER: GSE55462 | GEO | 2014/08/15

REPOSITORIES: GEO

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Project description:Background: Soil salinity is a major abiotic stress factor that limit agricultural productivity worldwide, and this problem is expected to grow in the future. Common bean (Phaseolus vulgaris L.) is an important protein source in developing countries is highly susceptible to salt stress. To understand the underlying mechanism of salt stress responses, transcriptomics, metabolomics, and ion content analysis were utilized for response comparison of salt-tolerant and salt-susceptible common bean genotypes in saline conditions. Results: Transcriptome analysis has revealed that the tolerant genotype had increased photosynthesis in saline conditions while the susceptible genotype acted in a contrasting way. The chlorophyll content measurements have backed up this result with increase in tolerant and decrease in susceptible genotype. Transcriptome also displayed a more active carbon and amino acid metabolism for the tolerant genotype as well. Analysis of primary metabolites with GC-MS demonstrated the boosted carbohydrate metabolism in the tolerant genotype with increased sugar content as well as better amino-acid metabolism with the accumulation of glutamate and asparagine and hinted a lowered photorespiration level for the tolerant one. Accumulation of lysine, valine, and isoleucine in the roots of the susceptible genotype suggested a halted stress response pathway. According to ion content comparison, the tolerant genotype managed to block accumulation of Na+ in the leaves while accumulating significantly less Na+ in the roots compared to susceptible genotype. K+ levels increased in the leaves of both genotype and the roots of the susceptible one but dropped in the roots of the tolerant genotype. Additionally, Zn+2 and Mn+2 levels were also dropped in the tolerant roots, while Mo+2 levels were significantly higher in all tissues in both control and saline conditions for tolerant genotype. Conclusion:The results of the presented study have demonstrated the differences in contrasting genotypes and thus provide valuable information on the pivotal molecular mechanisms underlying salt tolerance mainly in common bean, but for all crops.

Project description:‘Pulsechip’, a boutique cDNA microarray, generated from a set of chickpea (Cicer arietinum L.) unigenes, grasspea (Lathyrus sativus L.) ESTs and lentil (Lens culinaris Med.) resistance gene analogs, was employed to generate an expression profile of chickpea accessions tolerant and susceptible to high-salinity stress. Two groups of a tolerant and susceptible accession were challenged with high-salinity stress. The experiments were performed in three biological replications. The experiments were conducted in reference design where respective tissues from unstressed plants served as control. The leaf/shoot and root tissues were collected at 24 and 48 h post-treatment (hpt) and used for hybridization to measure changes in RNA abundance of treatment vs. control. The tissues from five experimental replicate plants per biological replication were pooled together (shoot and root tissues separate for each time point) before RNA extraction. This RNA was used to prepare cDNA targets for expression analysis using microarray. The microarray had six technical replicate spots per EST. The transcript level for each EST/cDNA was firstly calculated as the average intensity of the six technical replicates and then the average intensity of three biological replicates. Data analysis included LOWESS normalization (LOcally WEighted polynomial regreSSion) to adjust for differences in quantity of initial RNA, labeling and detection efficiencies. A dye swap in one biological replicate adjusted dye bias, if any. The Differentially Expressed (DE) ESTs were identified as those with a 95% confidence interval for mean fold change (FC) that extended beyond the two-fold cut-off and also passed the Students t test (P<0.05) and FDR correction. These cut-offs translate into induced ESTs having a log2 ratio > 1 and repressed ESTs a ratio of < -1. The analysis consisted of three fold comparison. Firstly, the ESTs that were differentially expressed between treatment and control plants of each accession were detected. Then the ESTs that were similarly expressed by tolerant and susceptible accessions were then eliminated by comparison. This included a two-way comparison, where tolerant and susceptible genotypes were compared within and between groups. Lastly, ESTs that were consensually differentially expressed between tolerant and susceptible accessions of the two batches were identified. The hypothesis was that if a putative gene was consistently expressed only in tolerant or susceptible genotype for a particular stress, it might be a candidate for tolerance/susceptibility for that stress. Globally, the level of 409 transcripts was affected in response to high-salinity stress in all the genotypes and tissue types studied. Of the transcripts consistently expressed in tolerant genotypes in response to high-salinity stress, the annotation of transcripts at 24 hpt suggest a reduction in energy production in shoots and roots by repression of putative genes including P700 chlorophyll a-apoprotein (DY475501) and NADH-plastoquinone oxidoreductase subunit I (DY475287), cytosolic fructose 1,6-bisphosphatase (DY475548) and splicing factor-like protein (DY396290). The ATHP3 (DY396300) and protein kinase (DY475077) that are potentially involved in signalling cascades responsible for sensing and relaying osmotic stress signals, were consistently repressed in tolerant genotypes in response to high-salinity. Additionally a glycine rich protein (DY396342) that is associated with lignification of cell walls in response to wounding and pathogen attack was repressed in tolerant genotypes. In tolerant genotypes at 48 hpt, two energy and metabolic-related transcripts were consistently repressed in roots, including a carbonic anhydrase (DY475403) and putative thiazole biosynthetic enzyme (DY475242). In shoots, only a pathogenesis-related protein (DY396301) was consistently repressed at 48 hpt, but a similar transcript (DY396281) was induced in roots of tolerant genotypes at the same time. Only four transcripts were DE in susceptible genotypes at 24 hpt, all occurring in root tissue. Two of these were unknown/unclear, but the others included a proline oxidase transcript (DY475225) and a nuclear transport factor 2 (DY396436). At 48 hpi, a putative splicing factor-like protein (DY396290) and polyubiquitin (DY396328) were repressed in roots of susceptible genotypes. Interstingly, a putative xylosidase (DY475408) was induced in susceptible roots at 48 hpi. Finally, several unknown/unclear transcripts were DE in both tolerant and susceptible genotypes. Of interest were two unknowns (DY475293 and DY475521) that were consistently expressed in tolerant genotypes and may be important for high-salinity tolerance. Keywords: Chickpea, High-salinity stress, tolerant, susceptible, cDNA microarray