Heat and drought induced transcriptomic changes in barley varieties with contrasting stress response phenotypes

Authors: Mahalingam, Ramamurthy; DUHAN, NAVEEN - Utah State University; KAUNDAL, RAKESH - Utah State University; SMERTENKO, ANDREI - Washington State University; NAZAROV, TARAS - Washington State University; Bregitzer, Paul

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2022
Publication Date: 12/8/2022
Citation: Mahalingam, R., Duhan, N., Kaundal, R., Smertenko, A., Nazarov, T., Bregitzer, P.P. 2022. Heat and drought induced transcriptomic changes in barley varieties with contrasting stress response phenotypes. Frontiers in Plant Science. 13. https://doi.org/10.3389/fpls.2022.1066421.
DOI: https://doi.org/10.3389/fpls.2022.1066421

Interpretive Summary: Plants growing under field conditions are often exposed to multiple abiotic factors such as water stress, temperature extremes, soil salinity and biotic factors such as pathogens, pests and parasites simultaneously or sequentially. Most basic research on stresses have dealt with a single stressor at a time. In recent years, the importance of conducting research on two or more stresses has gained traction. In this report we used a malting barley variety, Golden Promise that is sensitive to heat and drought stress and a feed barley variety Otis that is resistant to heat and drought. Plants were subjected to heat, drought or combined heat and drought stress during grain filling stage. The genes that were differentially expressed in response to single or combined stresses were identified. The sensitive variety exhibited massive changes in gene expression compared to the tolerant variety. Secondly, the gene expression changes in response to combined stress was more intense and were impacted within one day of stress initiation. The tolerant variety exhibited a more toned response to these stresses and this was due to innately higher levels of expression of genes that are associated with reducing oxidative stress. These genes were associated with synthesis of antioxidants, osmolytes such as proline and trehalose, and hormones such as jasmonic acid. Identification of key regulatory genes provides useful tools for marker assisted breeding or engineering barley to be more resilient to heat and drought stresses.

Technical Abstract: Water deficit and heat stress substantially influence plant growth and productivity. When occurring individually, plants often exhibit reduced growth resulting in yield losses. The simultaneous occurrence of these stresses exacerbates their negative effects. Unraveling the molecular mechanisms of combined abiotic stress responses is essential to breed climate-resilient crops. In this study, transcriptome profiles were compared between stress-tolerant (Otis) and stress-sensitive (Golden Promise) barley genotypes subjected to drought, heat, and combined heat and drought stress for five days during heading stage. The major differences that emerged from the transcriptome analysis were the overall number of differentially expressed genes was relatively higher in Golden Promise (GP) compared to Otis. The differential expression of more than 900 transcription factors in GP and Otis may aid this transcriptional reprogramming in response to Otis. Secondly, combined heat and water deficit stress results in a unique and massive transcriptomic response that cannot be predicted from individual stress responses. Enrichment analyses of gene ontology terms revealed unique and stress type-specific adjustments of gene expression. Weighted Gene Co-expression Network Analysis identified genes associated with RNA metabolism and Hsp70 chaperone components as hub genes that can be useful for engineering tolerance to multiple abiotic stresses. Comparison of the transcriptomes of unstressed Otis and GP plants identified several genes associated with biosynthesis of antioxidants and osmolytes were higher in the former that maybe providing innate tolerance capabilities to effectively combat hostile conditions. Lines with different repertoire of innate tolerance mechanisms can be effectively leveraged in breeding programs for developing climate-resilient barley varieties with superior end-use traits.