Sorghum bicolor’s Transcriptome Response to Dehydration, High Salinity and ABA

Abstract

Genome wide changes in gene expression were monitored in the drought tolerant C4 cereal Sorghum bicolor, following exposure of seedlings to high salinity (150 mM NaCl), osmotic stress (20% polyethylene glycol) or abscisic acid (125 microM ABA). A sorghum cDNA microarray providing data on 12,982 unique gene clusters was used to examine gene expression in roots and shoots at 3- and 27-h post-treatment. Expression of approximately 2200 genes, including 174 genes with currently unknown functions, of which a subset appear unique to monocots and/or sorghum, was altered in response to dehydration, high salinity or ABA. The modulated sorghum genes had homology to proteins involved in regulation, growth, transport, membrane/protein turnover/repair, metabolism, dehydration protection, reactive oxygen scavenging, and plant defense. Real-time PCR was used to quantify changes in relative mRNA abundance for 333 genes that responded to ABA, NaCl or osmotic stress. Osmotic stress inducible sorghum genes identified for the first time included a beta-expansin expressed in shoots, actin depolymerization factor, inositol-3-phosphate synthase, a non-C4 NADP-malic enzyme, oleosin, and three genes homologous to 9-cis-epoxycarotenoid dioxygenase that may be involved in ABA biosynthesis. Analysis of response profiles demonstrated the existence of a complex gene regulatory network that differentially modulates gene expression in a tissue- and kinetic-specific manner in response to ABA, high salinity and water deficit. Modulation of genes involved in signal transduction, chromatin structure, transcription, translation and RNA metabolism contributes to sorghum's overlapping but nonetheless distinct responses to ABA, high salinity, and osmotic stress. Overall, this study provides a foundation of information on sorghum's osmotic stress responsive gene complement that will accelerate follow up biochemical, QTL and comparative studies.

Regulation of Sucrose Transporters and Phloem Loading in Response to Environmental Cues

“…In contrast to nonstressed conditions, when phloem loading rate and SUT expression seems to be a function of leaf sugar status (Vaughn et al, 2002, and results presented above), more complex patterns were observed under stress, probably reflecting the changes in water status and sink activity. Drought and salt stress were found to have the same effect on SUT expression in all species, which is not surprising considering the overlap of plant responses to osmotic stresses such as drought, and salinity shown in genomics studies (Kreps et al, 2002;Buchanan et al, 2005). The common pattern shows that both require the same adaptations regarding the transport of sugars.…”

Transcriptome Analysis of Drought Induced Stress in <i>Chenopodium quinoa</i>

“…Transcriptome research conducted in Arabidopsis thaliana [21,22], Oryza sativa [23,24], and Sorghum bicolor [25] has been used to successfully identify differentially expressed genes, implicating several biosynthetic pathways that assist in the overall tolerance to drought stress. Recent genomic research in quinoa has successfully identified genes (e.g., SOS1, NHX1, etc.)…”

Identification and profiling of salinity stress-responsive proteins in Sorghum bicolor seedlings

“…As such, sorghum offers great potential as a food source in both dry and relatively more saline regions. Several studies have been reported on the large scale screening of sorghum varieties for salt tolerance [24], transcriptome changes in response to dehydration and high salinity [25], the evaluation of growth parameters and ion accumulation [26], and soluble carbohydrate contents [27,28] among various cultivars of sorghum. Although these studies provide valuable information on the effect of salt stress on gene expression, plant growth and the accumulation of soluble sugars which may function as osmoprotectants, there is need to identify specific proteins that contribute to sorghum's salt tolerance mechanisms.…”