Drought stress tolerance strategies revealed by RNA-Seq in two sorghum genotypes with contrasting WUE

Abstract

BackgroundDrought stress is the major environmental stress that affects plant growth and productivity. It triggers a wide range of responses detectable at molecular, biochemical and physiological levels. At the molecular level the response to drought stress results in the differential expression of several metabolic pathways. For this reason, exploring the subtle differences in gene expression of drought sensitive and drought tolerant genotypes enables the identification of drought-related genes that could be used for selection of drought tolerance traits. Genome-wide RNA-Seq technology was used to compare the drought response of two sorghum genotypes characterized by contrasting water use efficiency.ResultsThe physiological measurements carried out confirmed the drought sensitivity of IS20351 and the drought tolerance of IS22330 genotypes, as previously studied. The expression of drought-related genes was more abundant in the drought sensitive genotype IS20351 compared to the tolerant genotype IS22330. Under drought stress Gene Ontology enrichment highlighted a massive increase in transcript abundance in the sensitive genotype IS20351 in “response to stress” and “abiotic stimulus”, as well as for “oxidation-reduction reaction”. “Antioxidant” and “secondary metabolism”, “photosynthesis and carbon fixation process”, “lipids” and “carbon metabolism” were the pathways most affected by drought in the sensitive genotype IS20351. In addition, genotype IS20351 showed a lower constitutive expression level of “secondary metabolic process” (GO:0019748) and “glutathione transferase activity” (GO:000004364) under well-watered conditions.ConclusionsRNA-Seq analysis proved to be a very useful tool to explore differences between sensitive and tolerant sorghum genotypes. Transcriptomics analysis results supported all the physiological measurements and were essential to clarify the tolerance of the two genotypes studied. The connection between differential gene expression and physiological response to drought unequivocally revealed the drought tolerance of genotype IS22330 and the strategy adopted to cope with drought stress.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0800-x) contains supplementary material, which is available to authorized users.

Transcriptomic Changes of Drought-Tolerant and Sensitive Banana Cultivars Exposed to Drought Stress

“…More number of unigenes was either up or down-regulated in DS than DT indicating sensitive genotypes were relatively hyper-responsive to stress and or easily disturbed by drought stress at molecular level. Our findings supports the reports of Yates et al (2014) and Fracasso et al (2016) who observed drought-sensitive genotypes of other plants (Clover and Sorghum) were found to be hyper-responsive to drought stress in comparison to their respective tolerant genotypes. This may be an indicative of absence of some transient and or primary layer of stress avoidance mechanism in sensitive cultivars to mitigate drought effects.…”

“…However, greater extent of reduction of TFs was noted in DT is not clear and information such as identification of precise target genes and regulatory pathways and their consequences may be essential to further understanding. Very recently Fracasso et al (2016) too found that TFs were largely reduced in tolerant sorghum genotypes than sensitive genotypes under drought stress conditions. Around 46 TF families including MYB, NAC, WRKY, bHLH, bZIP, ERF, and HSFs were differentially expressed in banana cultivars to drought stress ( Figure 8 ).…”

Real-Time Determination of Photosynthesis, Transpiration, Water-Use Efficiency and Gene Expression of Two Sorghum bicolor (Moench) Genotypes Subjected to Dry-Down

“…Whole-canopy WUE i values were different from WUE i calculated at leaf level in Fracasso et al (2016b). While at leaf level WUE i of WS plants decreased according to decreasing FTSW, at whole-canopy level WUE i of WS plants increased with the decreasing FTSW.…”

The ratio of trichomes to stomata is associated with water use efficiency in Solanum lycopersicum (tomato)

“…We observed a lower WUE i for IL 4‐1 under WD conditions compared with the other lines under study (Table ), whereas WUE i in IL 11‐3 was higher under WD compared with WW conditions (Table ). This increase in WUE i has been reported in drought‐tolerant varieties in several crops (Guha et al ., ; Fracasso et al ., ; Liu et al ., ), although it might not always have a positive effect on fruit yield. Interestingly, none of the ILs under study were considered before for WUE improvement as they showed no differences in δ 13 C compared with M82 (Xu et al ., ), in agreement with our results, so this epidermis‐based analysis provides an alternative path for increased WUE.…”