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Comparative Study
. 2012 Nov 29:13:680.
doi: 10.1186/1471-2164-13-680.

Comparative transcriptomic analysis of roots of contrasting Gossypium herbaceum genotypes revealing adaptation to drought

Alok Ranjan  1 , Neha Pandey, Deepika Lakhwani, Neeraj Kumar Dubey, Uday V Pathre, Samir V Sawant
Affiliations
Comparative Study

Comparative transcriptomic analysis of roots of contrasting Gossypium herbaceum genotypes revealing adaptation to drought

Alok Ranjan et al. BMC Genomics. .

Abstract

Background: Root length and its architecture govern the adaptability of plants to various stress conditions, including drought stress. Genetic variations in root growth, length, and architecture are genotypes dependent. In this study, we compared the drought-induced transcriptome of four genotypes of Gossypium herbaceum that differed in their drought tolerance adaptability. Three different methodologies, namely, microarray, pyrosequencing, and qRT-PCR, were used for transcriptome analysis and validation.

Results: The variations in root length and growth were found among four genotypes of G.herbaceum when exposed to mannitol-induced osmotic stress. Under osmotic stress, the drought tolerant genotypes Vagad and GujCot-21 showed a longer root length than did by drought sensitive RAHS-14 and RAHS-IPS-187. Further, the gene expression patterns in the root tissue of all genotypes were analyzed. We obtained a total of 794 differentially expressed genes by microarray and 104928 high-quality reads representing 53195 unigenes from the root transcriptome. The Vagad and GujCot-21 respond to water stress by inducing various genes and pathways such as response to stresses, response to water deprivation, and flavonoid pathways. Some key regulatory genes involved in abiotic stress such as AP2 EREBP, MYB, WRKY, ERF, ERD9, and LEA were highly expressed in Vagad and GujCot-21. The genes RHD3, NAP1, LBD, and transcription factor WRKY75, known for root development under various stress conditions, were expressed specifically in Vagad and GujCot-21. The genes related to peroxidases, transporters, cell wall-modifying enzymes, and compatible solutes (amino acids, amino sugars, betaine, sugars, or sugar alcohols) were also highly expressed in Vagad and Gujcot-21.

Conclusion: Our analysis highlights changes in the expression pattern of genes and depicts a small but highly specific set of drought responsive genes induced in response to drought stress. Some of these genes were very likely to be involved in drought stress signaling and adaptation, such as transmembrane nitrate transporter, alcohol dehydrogenase, pyruvate decarboxylase, sucrose synthase, and LEA. These results might serve as the basis for an in-depth genomics study of Gossypium herbaceum, including a comparative transcriptome analysis and the selection of genes for root traits and drought tolerance.

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Figures

Figure 1
Figure 1
Effect of osmotic stress induced by different percentages of mannitol in the hydroponics condition on the development of the root of Vagad, GujCot21, RAHS-14, and RAHS-IPS187.
Figure 2
Figure 2
GO annotation of differentially expressed up-regulated genes in RAHS-14 during control and drought conditions.
Figure 3
Figure 3
GO annotation of differentially expressed up-regulated genes in Vagad during drought and control conditions.
Figure 4
Figure 4
Validation of microarray differentially expressed genes by quantitative PCR. (A) Vagad (B) RAHS-14.
Figure 5
Figure 5
Gene ontology of differentially expressed contigs (fold change ≥ 2) in drought-tolerant (GujCot-21) and sensitive genotypes (RAHS-IPS-187). MF-molecular function, BP-Biological process.
Figure 6
Figure 6
Functional enrichment of differentially expressed contigs (fold change ≥ 2) by KOBAS (A) Tolerant genotype (GujCot-21) (B) Sensitive genotype (RAHS-IPS-187).
Figure 7
Figure 7
Differentially expressed TFs in all genotypes (Vagad, GujCot-21, RAHS-IPS-187 and RAHS-14).
Figure 8
Figure 8
DEGs are mapped by Genevestigator for tissue-specific expression analysis (A) tolerant and (B) sensitive genotype. On the basis of percentage expression potential of genes in different root zones obtained from heat map were given numbers and indicated in parenthesis with their description.
Figure 9
Figure 9
Differentially expressed genes (probe sets and contigs) analyzed by Genevestigator in mapping the specific expression of genes in different root zones.
See this image and copyright information in PMC

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