Unique Physiological and Transcriptional Shifts under Combinations of Salinity, Drought, and Heat

Abstract

Climate-change-driven stresses such as extreme temperatures, water deficit, and ion imbalance are projected to exacerbate and jeopardize global food security. Under field conditions, these stresses usually occur simultaneously and cause damages that exceed single stresses. Here, we investigated the transcriptional patterns and morpho-physiological acclimations of Brachypodium dystachion to single salinity, drought, and heat stresses, as well as their double and triple stress combinations. Hierarchical clustering analysis of morpho-physiological acclimations showed that several traits exhibited a gradually aggravating effect as plants were exposed to combined stresses. On the other hand, other morphological traits were dominated by salinity, while some physiological traits were shaped by heat stress. Response patterns of differentially expressed genes, under single and combined stresses (i.e. common stress genes), were maintained only among 37% of the genes, indicating a limited expression consistency among partially overlapping stresses. A comparison between common stress genes and genes that were uniquely expressed only under combined stresses (i.e. combination unique genes) revealed a significant shift from increased intensity to antagonistic responses, respectively. The different transcriptional signatures imply an alteration in the mode of action under combined stresses and limited ability to predict plant responses as different stresses are combined. Coexpression analysis coupled with enrichment analysis revealed that each gene subset was enriched with different biological processes. Common stress genes were enriched with known stress response pathways, while combination unique-genes were enriched with unique processes and genes with unknown functions that hold the potential to improve stress tolerance and enhance cereal productivity under suboptimal field conditions.

Phenotypic and metabolic plasticity shapes life‐history strategies under combinations of abiotic stresses

“…Plants subjected to S & H were able to sustain, for a longer period, higher or comparable values of chlorophyll content and F v / F m , respectively (Figs b, a), which further support the moderate decreases in photosynthesis rate, compared with control (Shaar‐Moshe et al., ). Under S & H, plants accumulated 29% less shoot DW, similar to D & H, yet the reproductive allocation was comparable to control conditions, indicating that the plants maintained source‐sink relationships and successfully partitioned photosynthetic assimilates to the reproductive tissues (Figure c,d).…”

“…This pattern was also reflected at the transcriptional level by a strong association between PSRI and senescence associated genes (SAG). In addition, a high correlation ( r = 0.97, p = 0.03) was detected between PSRI and genes involved in chloroplast nucleoid metabolism and maintenance (Supporting information Table ), a pathway that was enriched among genes uniquely expressed only under stress combinations (Shaar‐Moshe et al., ). The different PSRI values that were detected between S & H and S & D might be attributed to a higher carotenoid content under S & D, as chlorophyll contents were comparable under these stress combinations (Figs b, c).…”

“…Extraction of RNA from flag and second leaf samples and preparation of cDNA libraries and their sequencing were previously described in Shaar‐Moshe et al. (). Briefly, at 4 DAA, leaf samples were collected, frozen in liquid nitrogen and total RNA was extracted using Plant/Fungi Total RNA Purification Kit (Norgen Biotek Corp., Canada).…”

“…Recently we have shown a unique transcriptional signature among genes that were differentially expressed only under combinations of stresses. This transcriptional pattern was enriched with antagonistic responses, suggesting alterations in the mode of action under different combinations of stresses (Shaar‐Moshe et al., ). Here we used a system biology approach to test the hypothesis that plants elicit a unique acclimation strategy, with distinct trade‐offs in life‐history traits of growth, reproduction and defense under each combination.…”

Time‐course analysis of salicylic acid effects on ROS regulation and antioxidant defense in roots of hulled and hulless barley under combined stress of drought, heat and salinity

“…Nevertheless, plants are exposed to combinations of more than one stress in their natural habitats and agricultural systems. Recently, there has been an increase in the number of studies addressing stress combinations (Rivero et al , Suzuki et al , Shaar‐Moshe et al ). However, to date, no information has been found in the literature concerning exogenous application of a plant growth regulator to plants under the combined stress conditions of drought, heat and salt (DHS), or in particular, the physiological and biochemical effects of SA on barley seedling roots under the triple combination of DHS stress.…”