Sorghum genotypes exhibit adaptations to combined drought and salinity stress, through enhanced antioxidative defense, osmotic adjustment, and stress-responsive gene expression.

Keywords: Sorghum bicolor, abiotic resilience, genetic variation, oxidative stress mitigation, sustainable agriculture, targeted breeding

Researchers from King Abdulaziz University and Federal University Dutsinma investigated the integrated stress responses of sorghum to combined drought and salinity stress, revealing complex interactions among physiological, biochemical, and molecular mechanisms. Antioxidant enzyme activities, including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), varied among genotypes, highlighting genotype-specific defense strategies. Notably, CRS-01 exhibited lower SOD but higher CAT activity, suggesting differential oxidative stress regulation. Osmolyte accumulation, such as proline and glycine betaine, played a critical role in osmotic adjustment.  Sorghum genotypes CRS-01 and Samsorg-42 demonstrated  superior accumulation of osmolytes under stress conditions. Physiological parameters, including chlorophyll content, Na/K ratio, relative water content (RWC), and water potential, provided insights into stress tolerance, with CRS-01 maintaining favorable levels under severe drought and salinity stress. The decline in photosynthetic rate (Pn) and stomatal conductance (Gs) with increasing stress severity further underscored the trade-off between water conservation and carbon assimilation. However, Samsorg-17 exhibited consistently higher Pn and Gs, indicating its inherent resilience to abiotic stress.

At the molecular level, gene expression analysis highlighted the upregulation of key stress-related genes, including SbSOD1, SbAPX2, SbCAT3, SbHKT1; 4, SbDREB2A, SbDHN3, and SbPRP1, with the highest expression under combined stress conditions. Samsorg-17 displayed the strongest upregulation of these genes, correlating with its superior physiological and biochemical performance. Correlation and principal component analyses (PCA) revealed strong interdependencies among antioxidative defense mechanisms, osmotic regulation, and stress tolerance traits, emphasizing their collective role in mitigating oxidative stress and maintaining cellular homeostasis. Overall, these findings provide valuable insights into the adaptive strategies of sorghum under abiotic stress, guiding breeding efforts to develop more resilient cultivars for sustainable agriculture in arid and saline environments.

SorghumBase examples: 

This study demonstrates that SbDREB2A transcription factor is involved in enhancing stress tolerance by regulating gene expression in response to drought and salinity.  The DREB2A transcription factor was used as a keyword to search SorghumBase and the taxonomic distribution of the rice DREB2A gene provided its sorghum ortholog “SORBI_3003G058200”. This gene SORBI_3003G058200 was further used to explore its homology in other sorghum accessions and its expression across studies. 

Figure 1: Searching of the “DREB2A”gene displays the taxonomic distribution of this gene in 42 sorghum accessions including Sbi BTx623 V3 and V5 and in maize, rice, grapevine, Arabidopsis and Poplar along with outgroup Selaginella. The taxonomic distribution of “DREB2A” shows SORBI_3003G058200 in Sbi BTx623 V3 with 65% sequence identity to rice DREB2A gene. We selected SORBI_3003G058200; Sb03g004980, Sobic.003G058200, SbEREB45 similar to DRE-binding protein 2; 65% identity with its rice homolog) to further explore this gene in SorghumBase.
Figure 2: The sequence tab displays the peptide sequence of SORBI_3003G058200; Sb03g004980, Sobic.003G058200, SbEREB45 similar to DRE-binding protein 2) in the search results on SorghumBase. The figure also suggests the DREB2A as an ortholog of this gene with 65% identity.
Figure 3: This figure displays the chromosome location of SORBI_3003G058200; Sb03g004980, Sobic.003G058200, SbEREB45 similar to DRE-binding protein 2) under the Location tab in the Search results on SorghumBase. The gene is located on chromosome 3; within 3:5141395-5144094. In addition to SorghumBase, links are provided on to the internal SorghumBase Ensembl Browser and external resource Phytozome to explore this gene in detail.
Figure 4: This figure shows the expression profile of SORBI_3003G058200; Sb03g004980, Sobic.003G058200, SbEREB45 similar to DRE-binding proteinunder the Expression tab (All Studies) in the search display on SorghumBase. It displays the baseline expression of the gene across 10 published sorghum BTx623 datasets curated and processed by EMBL-EBI Expression Atlas in collaboration with the SorghumBase team.
Figure 5: This figure shows the homology of SORBI_3003G058200; Sb03g004980, Sobic.003G058200, SbEREB45 similar to DRE-binding protein 2) under the Homology tab in the SorghumBase. A total of 914 homologs that has 48 orthologs and 20 paralogs of this gene are identified.

Reference:

Alzahrani Y, Abdulbaki AS, Alsamadany H. Genotypic variability in stress responses of Sorghum bicolor under drought and salinity conditions. Front Genet. 2025 Jan 8;15:1502900. PMID: 39845188. doi: 10.3389/fgene.2024.1502900. Read more

Related Project Websites:

Adaptive Responses of Sorghum to Combined Drought and Salinity Stress: Physiological, Biochemical, and Molecular Insights

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