Cloning and characterization of a novel NAC family gene CarNAC1 from chickpea (Cicer arietinum L.)

Cloning and expression analysis of VrNAC13 gene in mung bean

To explore the role of NAC transcription factors in mung bean (Vigna ratiata), we here comprehensively analyzed VrNAC13 structure and expression patterns in the mung bean cultivar "Yulin No.1". The nucleotide sequence of VrNAC13 (GenBank accession number xp014518431.1) was determined by cloning and sequencing the gene. A predicted transcriptional activation domain in VrNAC13 was validated with a yeast one-hybrid assay. The composition and functional characteristics of VrNAC13 were analyzed using basic bioinformatics techniques, and the expression characteristics of VrNAC13 were analyzed via quantitative reverse transcription-PCR. The results showed that VrNAC13 was 1,068 bp in length and encoded a product of 355 amino acids. VrNAC13 was predicted to contain a NAM domain and to belong to the NAC transcription factor family. The protein was hydrophilic and contained several threonine phosphorylation sites. Phylogenetic analysis showed that VrNAC13 was highly similar in sequence to two Arabidopsis thaliana NAC proteins; we hypothesize that VrNAC13 may perform functions in mung bean similar to those of the two closely related proteins in Arabidopsis. Promoter analysis of VrNAC13 revealed cis-acting elements predicted to respond to abscisic acid (ABA), gibberellin, auxin, light, drought, low temperature, and other stressors. VrNAC13 was most highly expressed in the leaves and expressed at very low levels in the stem and root. It was experimentally determined to be induced by drought and ABA. Based on these results, VrNAC13 appears to regulate stress resistance in mung bean.

Ascochyta Blight in Chickpea: An Update

Chickpea (Cicer arietinum L.), one of the most cultivated legumes worldwide, is crucial for the economy of several countries and a valuable source of nutrients. Yields may be severely affected by Ascochyta blight, a disease caused by the fungus Ascochyta rabiei. Molecular and pathological studies have not yet managed to establish its pathogenesis, since it is highly variable. Similarly, much remains to be elucidated about plant defense mechanisms against the pathogen. Further knowledge of these two aspects is fundamental for the development of tools and strategies to protect the crop. This review summarizes up-to-date information on the disease's pathogenesis, symptomatology, and geographical distribution, as well as on the environmental factors that favor infection, host defense mechanisms, and resistant chickpea genotypes. It also outlines existing practices for integrated blight management.

AvNAC030, a NAC Domain Transcription Factor, Enhances Salt Stress Tolerance in Kiwifruit

Kiwifruit (Actinidia chinensis Planch) is suitable for neutral acid soil. However, soil salinization is increasing in kiwifruit production areas, which has adverse effects on the growth and development of plants, leading to declining yields and quality. Therefore, analyzing the salt tolerance regulation mechanism can provide a theoretical basis for the industrial application and germplasm improvement of kiwifruit. We identified 120 NAC members and divided them into 13 subfamilies according to phylogenetic analysis. Subsequently, we conducted a comprehensive and systematic analysis based on the conserved motifs, key amino acid residues in the NAC domain, expression patterns, and protein interaction network predictions and screened the candidate gene AvNAC030. In order to study its function, we adopted the method of heterologous expression in Arabidopsis. Compared with the control, the overexpression plants had higher osmotic adjustment ability and improved antioxidant defense mechanism. These results suggest that AvNAC030 plays a positive role in the salt tolerance regulation mechanism in kiwifruit.

Strawberry FaNAC2 Enhances Tolerance to Abiotic Stress by Regulating Proline Metabolism

The quality and yields of strawberry plants are seriously affected by abiotic stress every year. NAC (NAM, ATAF, CUC) transcription factors are plant-specific, having various functions in plant development and response to stress. In our study, FaNAC2 from strawberry (Fragaria × ananassa, cultivar "Benihoppe") was isolated and found to be a member of the ATAF sub-family, belonging to the NAC family of transcription factors. FaNAC2 was strongly expressed in the shoot apical meristem and older leaves of strawberries, and was induced by cold, high salinity, and drought stress. To investigate how FaNAC2 functions in plant responses to abiotic stress, transgenic Nicotiana benthamiana plants ectopically overexpressing FaNAC2 were generated. The transgenic plants grew better under salt and cold stress, and, during simulated drought treatment, these transgenic lines not only grew better, but also showed higher seed germination rates than wild-type plants. Gene expression analysis revealed that key genes in proline biosynthesis pathways were up-regulated in FaNAC2 overexpression lines, while its catabolic pathway genes were down-regulated and proline was accumulated more with the overexpression of FaNAC2 after stress treatments. Furthermore, the gene expression of abscisic acid biosynthesis was also promoted. Our results demonstrate that FaNAC2 plays an important positive role in response to different abiotic stresses and may be further utilized to improve the stress tolerance of strawberry plants.

A novel Miscanthus NAC transcription factor MlNAC10 enhances drought and salinity tolerance in transgenic Arabidopsis

NAC (NAM, ATAF1/2 and CUC2) proteins are key regulators of various plant stress tolerances. However, knowledge of NAC genes remains largely unknown in Miscanthus. Here, we characterized a novel NAC gene MlNAC10 from M. lutarioriparius than plays a role in abiotic stress tolerance. MlNAC10 encodes a nuclear-localized protein with a C-terminal transactivation domain, and has a specific binding affinity to the NAC recognition sequence (NACRS). Ectopic expression of MlNAC10 in Arabidopsis led to increased sensitivity to abscisic acid (ABA) at early seedling growth stages. In addition, the proline content was significantly increased and the reactive oxygen species (ROS) scavenging capability was significantly enhanced in MlNAC10 overexpression lines under ABA treatment. Moreover, the drought and salt stress tolerance was significantly improved in MlNAC10 overexpression lines. Consistently, the activities of three antioxidant enzymes, namely catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), were dramatically stimulated in the overexpression lines compared to the wild type (WT). Correspondingly, the accumulation of ROS was dramatically decreased and malondialdehyde (MDA) was accumulated at a much lower level in the transgenic lines. Meanwhile, the expression of six abiotic stress-related genes was dramatically stimulated in the overexpression lines in comparison to the WT. Together, our results demonstrated that MlNAC10 acts as an important regulator of drought and salinity stress tolerance by stimulating antioxidant enzymes and alleviating ROS damage via the ABA signaling pathway.

Improving Salt Tolerance of Chickpea Using Modern Genomics Tools and Molecular Breeding

INTRODUCTION

The high protein value, essential minerals, dietary fibre and notable ability to fix atmospheric nitrogen make chickpea a highly remunerative crop, particularly in low-input food production systems. Of the variety of constraints challenging chickpea productivity worldwide, salinity remains of prime concern owing to the intrinsic sensitivity of the crop. In view of the projected expansion of chickpea into arable and salt-stressed land by 2050, increasing attention is being placed on improving the salt tolerance of this crop. Considerable effort is currently underway to address salinity stress and substantial breeding progress is being made despite the seemingly highly-complex and environment-dependent nature of the tolerance trait.

CONCLUSION

This review aims to provide a holistic view of recent advances in breeding chickpea for salt tolerance. Initially, we focus on the identification of novel genetic resources for salt tolerance via extensive germplasm screening. We then expand on the use of genome-wide and cost-effective techniques to gain new insights into the genetic control of salt tolerance, including the responsive genes/QTL(s), gene(s) networks/cross talk and intricate signalling cascades.

Defence gene expression profiling to Ascochyta rabiei aggressiveness in chickpea

Significant differences in defence pathway-related gene expression were observed among chickpea cultivars following A. rabiei infection. Differential gene expression is indicative of diverse resistances, a theoretical tool for selective breeding. A high number of Ascochyta rabiei pathotypes infecting chickpea in Australia has severely hampered efforts towards breeding for sustained quantitative resistance in chickpea. Breeding for sustained resistance will be aided by detailed knowledge of defence responses to isolates with different aggressiveness. As an initial step, the conserved and differential expressions of a suit of previously characterised genes known to be involved in fungal defence mechanisms were assessed among resistant and susceptible host genotypes following inoculation with high or low aggressive A. rabiei isolates. Using quantitative Real-Time PCR (qRT-PCR), 15 defence-related genes, normalised with two reference genes, were temporally differentially expressed (P < 0.005) as early as 2 h post inoculation of Genesis090 (resistant) or Kaniva (susceptible). The highly aggressive isolate, 09KAL09, induced vastly different expression profiles of eight key defence-related genes among resistant and susceptible genotypes. Six of these same genes were differentially expressed among ten host genotypes, inclusive of the best resistance sources within the Australian chickpea breeding program, indicating potential use for discrimination and selection of resistance "type" in future breeding pursuits.

Comprehensive analysis suggests overlapping expression of rice ONAC transcription factors in abiotic and biotic stress responses

NAC (NAM/ATAF/CUC) transcription factors comprise a large plant-specific gene family that contains more than 149 members in rice. Extensive studies have revealed that NAC transcription factors not only play important roles in plant growth and development, but also have functions in regulation of responses to biotic and abiotic stresses. However, biological functions for most of the members in the NAC family remain unknown. In this study, microarray data analyses revealed that a total of 63 ONAC genes exhibited overlapping expression patterns in rice under various abiotic (salt, drought, and cold) and biotic (infection by fungal, bacterial, viral pathogens, and parasitic plants) stresses. Thirty-eight ONAC genes exhibited overlapping expression in response to any two abiotic stresses, among which 16 of 30 selected ONAC genes were upregulated in response to exogenous ABA. Sixty-five ONAC genes showed overlapping expression patterns in response to any two biotic stresses. Results from the present study suggested that members of the ONAC genes with overlapping expression pattern may have pleiotropic biological functions in regulation of defense response against different abiotic and biotic stresses, which provide clues for further functional analysis of the ONAC genes in stress tolerance and pathogen resistance.

Characterization and expression profile of CaNAC2 pepper gene

The plant-specific NAC (NAM, ATAF, and CUC) transcription factors have diverse role in development and stress regulation. A new transcript encoding NAC protein, homologous to nam-like protein 4 from Petunia was identified from an ABA-regulated subtractive cDNA library of Capsicum annuum seedling. Here, this homolog (named CaNAC2) from C. annuum was characterized and investigated its role in abiotic stress tolerance. Our results indicated that a plant-specific and conserved NAC domain was located in the N-terminus domain of CaNAC2 which was predicted to encode a polypeptide of 410 amino acids. Phylogenetic analysis showed that CaNAC2 belonged to the NAC2 subgroup of the orthologous group 4d. The protein CaNAC2 was subcellularly localized in the nucleus and it had transcriptional activity in yeast cell. CaNAC2 was expressed mainly in seed and root. The transcription expression of CaNAC2 was strongly induced by cold, salt and ABA treatment and inhibited by osmotic stress and SA treatment. Silence of CaNAC2 in virus-induced gene silenced pepper seedlings resulted in the increased susceptibility to cold stress and delayed the salt-induced leaf chlorophyll degradation. These results indicated that this novel CaNAC2 gene might be involved in pepper response to abiotic stress tolerance.

Genomics-assisted breeding for drought tolerance in chickpea

Terminal drought is one of the major constraints in chickpea (Cicer arietinum L.), causing more than 50% production losses. With the objective of accelerating genetic understanding and crop improvement through genomics-assisted breeding, a draft genome sequence has been assembled for the CDC Frontier variety. In this context, 544.73Mb of sequence data were assembled, capturing of 73.8% of the genome in scaffolds. In addition, large-scale genomic resources including several thousand simple sequence repeats and several million single nucleotide polymorphisms, high-density diversity array technology (15360 clones) and Illumina GoldenGate assay genotyping platforms, high-density genetic maps and transcriptome assemblies have been developed. In parallel, by using linkage mapping approach, one genomic region harbouring quantitative trait loci for several drought tolerance traits has been identified and successfully introgressed in three leading chickpea varieties (e.g. JG 11, Chefe, KAK 2) by using a marker-assisted backcrossing approach. A multilocation evaluation of these marker-assisted backcrossing lines provided several lines with 10-24% higher yield than the respective recurrent parents.Modern breeding approaches like marker-assisted recurrent selection and genomic selection are being deployed for enhancing drought tolerance in chickpea. Some novel mapping populations such as multiparent advanced generation intercross and nested association mapping populations are also being developed for trait mapping at higher resolution, as well as for enhancing the genetic base of chickpea. Such advances in genomics and genomics-assisted breeding will accelerate precision and efficiency in breeding for stress tolerance in chickpea.

Banana fruit NAC transcription factor MaNAC1 is a direct target of MaICE1 and involved in cold stress through interacting with MaCBF1

Our previous studies have indicated that the banana ripening-induced MaNAC1, a NAC (NAM, ATAF1/2 and CUC2) transcription factor (TF) gene, is regulated by ethylene during fruit ripening, and propylene, a functional ethylene analogue, induces cold tolerance of banana fruits. However, the involvement of MaNAC1 in propylene-induced cold tolerance of banana fruits is not understood. In the present work, the possible involvement of MaNAC1 in cold tolerance of banana fruits was investigated. MaNAC1 was noticeably induced by cold stress or following propylene treatment during cold storage. Transient protoplast assays showed that MaNAC1 promoter was activated by cold stress and ethylene treatment. Yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA) and transient expression assays demonstrated MaNAC1 as a novel direct target of MaICE1, and that the ability of MaICE1 binding to MaNAC1 promoter might be enhanced by MaICE1 phosphorylation and cold stress. Moreover, yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) analyses revealed physical interaction between MaNAC1 and MaCBF1, a downstream component of inducer of C-repeat binding factor (CBF) expression 1 (ICE1) in cold signalling. Taken together, these results suggest that the cold-responsive MaNAC1 may be involved in cold tolerance of banana fruits through its interaction with ICE1-CBF cold signalling pathway, providing new insights into the regulatory activity of NAC TF.

Genome-wide analysis of drought induced gene expression changes in flax (Linum usitatissimum)

A robust phenotypic plasticity to ward off adverse environmental conditions determines performance and productivity in crop plants. Flax (linseed), is an important cash crop produced for natural textile fiber (linen) or oilseed with many health promoting products. This crop is prone to drought stress and yield losses in many parts of the world. Despite recent advances in drought research in a number of important crops, related progress in flax is very limited. Since, response of this plant to drought stress has not been addressed at the molecular level; we conducted microarray analysis to capture transcriptome associated with induced drought in flax. This study identified 183 differentially expressed genes (DEGs) associated with diverse cellular, biophysical and metabolic programs in flax. The analysis also revealed especially the altered regulation of cellular and metabolic pathways governing photosynthesis. Additionally, comparative transcriptome analysis identified a plethora of genes that displayed differential regulation both spatially and temporally. These results revealed co-regulated expression of 26 genes in both shoot and root tissues with implications for drought stress response. Furthermore, the data also showed that more genes are upregulated in roots compared to shoots, suggesting that roots may play important and additional roles in response to drought in flax. With prolonged drought treatment, the number of DEGs increased in both tissue types. Differential expression of selected genes was confirmed by qRT-PCR, thus supporting the suggested functional association of these intrinsic genes in maintaining growth and homeostasis in response to imminent drought stress in flax. Together the present study has developed foundational and new transcriptome data sets for drought stress in flax.

Identification of key drought stress-related genes in the hyacinth bean

Hyacinth bean (Lablab purpureus [Linn.] Sweet) possesses excellent characteristics for field production, but the response of this plant to drought stress has not been described at the molecular level. Suppression subtraction hybridization (SSH) is an effective way to exploit key factors for plant responses to drought stress that are involved in transcriptional and metabolic activities. In this study, forward and reverse SSH libraries were generated from root tissues of the drought-tolerant hyacinth bean genotype MEIDOU 2012 under water-stress conditions. A total of 1,287 unigenes (94 contigs and 1,193 singletons) were derived from sequence alignment and cluster assembly of 1400 ESTs, and 80.6% of those hit against NCBI non-redundant (nr) database with E value <1E-06. BLASTX analysis revealed that the majority top matches were proteins form Glycine max (L.) Merrill. (61.5%). According to a gene ontology (GO) functional classification, 816 functionally annotated unigenes were assigned to the biological process category (74.1%), and 83.9% of them classified into molecular function and 69.2% involved in cellular component. A total of 168 sequences were further annotated with 207 Enzyme Commission (EC) codes and mapped to 83 different KEGG pathways. Seventeen functionally relevant genes were found to be overrepresented under drought stress using enrichment analysis. Differential expression of unigenes were confirmed by quantitative real-time PCR assays, and their transcript profiles generally divided into three patterns, depending on the expression peaked levels after 6, 8 or 10 days dehydration, which indicated that these genes are functionally associated in the drought-stress response.

Transcriptome-wide survey and expression analysis of stress-responsive NAC genes in Chrysanthemum lavandulifolium

The plant-specific NAC (NAM, ATAF, and CUC) transcription factor family plays a vital role in various plant growth and developmental processes as well as in stress resistance. Using RNA sequencing, we found that the ClNAC genes (ClNAC1-44) were the most strongly up-regulated transcription factor family in Chrysanthemum lavandulifolium leaves under salt treatment. We carried out reverse transcriptase polymerase chain reaction to monitor ClNAC genes response against multiple stresses and hormonal treatments including salt, drought, cold, heat, abscisic acid and salicylic acid treatments. The results showed that 35 ClNAC genes were differentially expressed in different organ, and 32 ClNAC genes could respond to at least 2 kinds of treatments. Quantitative real time polymerase chain reaction showed that 10 ClNAC genes belonging to 7 different subfamilies could respond to at least 5 kinds of treatments. Over 50-fold variation in transcriptional levels of ClNAC17 and ClNAC21 genes was observed under 6 different types of treatments. In the present study, high-level expression of ClNAC genes under abiotic stresses and hormonal treatments suggests that the NAC transcription factors play important roles in abiotic stress tolerance and adaptation.

Transcriptional responses to drought stress in root and leaf of chickpea seedling

Chickpea (Cicer arietinum L.) is an important pulse crop grown mainly in the arid and semi-arid regions of the world. Due to its taxonomic proximity with the model legume Medicago truncatula and its ability to grow in arid soil, chickpea has its unique advantage to understand how plant responds to drought stress. In this study, an oligonucleotide microarray was used for analyzing the transcriptomic profiles of unigenes in leaf and root of chickpea seedling under drought stress, respectively. Microarray data showed that 4,815 differentially expressed unigenes were either ≥ 2-fold up- or ≤ 0.5-fold down-regulated in at least one of the five time points during drought stress. 2,623 and 3,969 unigenes were time-dependent differentially expressed in root and leaf, respectively. 110 pathways in two tissues were found to respond to drought stress. Compared to control, 88 and 52 unigenes were expressed only in drought-stressed root and leaf, respectively, while nine unigenes were expressed in both the tissues. 1,922 function-unknown unigenes were found to be remarkably regulated by drought stress. The expression profiles of these time-dependent differentially expressed unigenes were useful in furthering our knowledge of molecular mechanism of plant in response to drought stress.

Molecular cloning and characterization of a membrane associated NAC family gene, SiNAC from foxtail millet [Setaria italica (L.) P. Beauv]

The plant-specific NAC (NAM, ATAF, and CUC) transcription factors have diverse role in development and stress regulation. A transcript encoding NAC protein, termed SiNAC was identified from a salt stress subtractive cDNA library of S. italica seedling (Puranik et al., J Plant Physiol 168:280-287, 2011). This single/low copy gene containing four exons and four introns within the genomic-sequence encoded a protein of 462 amino acids. Structural analysis revealed that highly divergent C terminus contains a transmembrane domain. The NAC domain consisted of a twisted antiparallel beta-sheet packing against N terminal alpha helix on one side and a shorter helix on the other side. The domain was predicted to homodimerize and control DNA-binding specificity. The physicochemical features of the SiNAC homodimer interface justified the dimeric form of the predicted model. A 1539 bp fragment upstream to the start codon of SiNAC gene was cloned and in silico analysis revealed several putative cis-acting regulatory elements within the promoter sequence. Transactivation analysis indicated that SiNAC activated expression of reporter gene and the activation domain lied at the C terminal. The SiNAC:GFP was detected in the nucleus and cytoplasm while SiNAC ΔC(1-158):GFP was nuclear localized in onion epidermal cells. SiNAC transcripts mostly accumulated in young spikes and were strongly induced by dehydration, salinity, ethephon, and methyl jasmonate. These results suggest that SiNAC encodes a membrane associated NAC-domain protein that may function as a transcriptional activator in response to stress and developmental regulation in plants.

Gene discovery and tissue-specific transcriptome analysis in chickpea with massively parallel pyrosequencing and web resource development

Chickpea (Cicer arietinum) is an important food legume crop but lags in the availability of genomic resources. In this study, we have generated about 2 million high-quality sequences of average length of 372 bp using pyrosequencing technology. The optimization of de novo assembly clearly indicated that hybrid assembly of long-read and short-read primary assemblies gave better results. The hybrid assembly generated a set of 34,760 transcripts with an average length of 1,020 bp representing about 4.8% (35.5 Mb) of the total chickpea genome. We identified more than 4,000 simple sequence repeats, which can be developed as functional molecular markers in chickpea. Putative function and Gene Ontology terms were assigned to at least 73.2% and 71.0% of chickpea transcripts, respectively. We have also identified several chickpea transcripts that showed tissue-specific expression and validated the results using real-time polymerase chain reaction analysis. Based on sequence comparison with other species within the plant kingdom, we identified two sets of lineage-specific genes, including those conserved in the Fabaceae family (legume specific) and those lacking significant similarity with any non chickpea species (chickpea specific). Finally, we have developed a Web resource, Chickpea Transcriptome Database, which provides public access to the data and results reported in this study. The strategy for optimization of de novo assembly presented here may further facilitate the transcriptome sequencing and characterization in other organisms. Most importantly, the data and results reported in this study will help to accelerate research in various areas of genomics and implementing breeding programs in chickpea.

Overexpression of TaNAC69 leads to enhanced transcript levels of stress up-regulated genes and dehydration tolerance in bread wheat

NAC proteins are plant-specific transcription factors and enriched with members involved in plant response to drought stress. In this study, we analyzed the expression profiles of TaNAC69 in bread wheat using Affymetrix Wheat Genome Array datasets and quantitative RT-PCR. TaNAC69 expression was positively associated with wheat responses to both abiotic and biotic stresses and was closely correlated with a number of stress up-regulated genes. The functional analyses of TaNAC69 in transgenic wheat showed that TaNAC69 driven by a barley drought-inducible HvDhn4s promoter led to marked drought-inducible overexpression of TaNAC69 in the leaves and roots of transgenic lines. The HvDhn4s:TaNAC69 transgenic lines produced more shoot biomass under combined mild salt stress and water-limitation conditions, had longer root and more root biomass under polyethylene glycol-induced dehydration. Analysis of transgenic lines with constitutive overexpression of TaNAC69 showed the enhanced expression levels of several stress up-regulated genes. DNA-binding assays revealed that TaNAC69 and its rice homolog (ONAC131) were capable of binding to the promoter elements of three rice genes (chitinase, ZIM, and glyoxalase I) and an Arabidopsis glyoxalase I family gene, which are homologs of TaNAC69 up-regulated stress genes. These data suggest that TaNAC69 is involved in regulating stress up-regulated genes and wheat adaptation to drought stress.

Comparative analysis of expressed sequence tags (ESTs) between drought-tolerant and -susceptible genotypes of chickpea under terminal drought stress

BACKGROUND

Chickpea (Cicer arietinum L.) is an important grain-legume crop that is mainly grown in rainfed areas, where terminal drought is a major constraint to its productivity. We generated expressed sequence tags (ESTs) by suppression subtraction hybridization (SSH) to identify differentially expressed genes in drought-tolerant and -susceptible genotypes in chickpea.

RESULTS

EST libraries were generated by SSH from root and shoot tissues of IC4958 (drought tolerant) and ICC 1882 (drought resistant) exposed to terminal drought conditions by the dry down method. SSH libraries were also constructed by using 2 sets of bulks prepared from the RNA of root tissues from selected recombinant inbred lines (RILs) (10 each) for the extreme high and low root biomass phenotype. A total of 3062 unigenes (638 contigs and 2424 singletons), 51.4% of which were novel in chickpea, were derived by cluster assembly and sequence alignment of 5949 ESTs. Only 2185 (71%) unigenes showed significant BLASTX similarity (<1E-06) in the NCBI non-redundant (nr) database. Gene ontology functional classification terms (BLASTX results and GO term), were retrieved for 2006 (92.0%) sequences, and 656 sequences were further annotated with 812 Enzyme Commission (EC) codes and were mapped to 108 different KEGG pathways. In addition, expression status of 830 unigenes in response to terminal drought stress was evaluated using macro-array (dot blots). The expression of few selected genes was validated by northern blotting and quantitative real-time PCR assay.

CONCLUSION

Our study compares not only genes that are up- and down-regulated in a drought-tolerant genotype under terminal drought stress and a drought susceptible genotype but also between the bulks of the selected RILs exhibiting extreme phenotypes. More than 50% of the genes identified have been shown to be associated with drought stress in chickpea for the first time. This study not only serves as resource for marker discovery, but can provide a better insight into the selection of candidate genes (both up- and downregulated) associated with drought tolerance. These results can be used to identify suitable targets for manipulating the drought-tolerance trait in chickpea.