Time of day and genotype sensitivity adjust molecular responses to temperature stress in sorghum

• Published in: The Plant journal : for cell and molecular biology Vol. 116; no. 4; pp. 1081 - 1096
• Main Authors: Bonnot, Titouan, Somayanda, Impa, Jagadish, S. V. Krishna, Nagel, Dawn H.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.11.2023; Wiley
• Subjects: Calcium ions; Circadian rhythms; Crop resilience; Crops; EF-hand; Gene expression; Genes; Genotype & phenotype; Genotypes; Hand protein; Life Sciences; Molecular dynamics; Sensitivity; Sorghum; Temperature tolerance; Time of use; temperature stress; co-expression; transcriptome; time of day
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.16467

SUMMARY Sorghum is one of the four major C4 crops that are considered to be tolerant to environmental extremes. Sorghum shows distinct growth responses to temperature stress depending on the sensitivity of the genetic background. About half of the transcripts in sorghum exhibit diurnal rhythmic expressions emphasizing significant coordination with the environment. However, an understanding of how molecular dynamics contribute to genotype‐specific stress responses in the context of the time of day is not known. We examined whether temperature stress and the time of day impact the gene expression dynamics in thermo‐sensitive and thermo‐tolerant sorghum genotypes. We found that time of day is highly influencing the temperature stress responses, which can be explained by the rhythmic expression of most thermo‐responsive genes. This effect is more pronounced in thermo‐tolerant genotypes, suggesting a stronger regulation of gene expression by the time of day and/or by the circadian clock. Genotypic differences were mostly observed on average gene expression levels, which may be responsible for contrasting sensitivities to temperature stress in tolerant versus susceptible sorghum varieties. We also identified groups of genes altered by temperature stress in a time‐of‐day and genotype‐specific manner. These include transcriptional regulators and several members of the Ca 2+ ‐binding EF‐hand protein family. We hypothesize that expression variation of these genes between genotypes along with time‐of‐day independent regulation may contribute to genotype‐specific fine‐tuning of thermo‐responsive pathways. These findings offer a new opportunity to selectively target specific genes in efforts to develop climate‐resilient crops based on their time‐of‐day and genotype variation responses to temperature stress. Significance Statement We report the diurnal gating of temperature stress responses in sorghum, a C4 crop. We investigated whether there is time of day control on the molecular response to heat and cold stress in thermo‐tolerant and thermo‐sensitive genotypes. We observe that the responses of the thermo‐tolerant genotypes are more influenced by time of day, and identified genes that exhibit significant differences between the selected genotypes that may be ideal targets for genetic manipulation in select varieties.