Effect of terminal heat stress on osmolyte accumulation and gene expression during grain filling in bread wheat (Triticum aestivum L.)

Abstract

The grain‐filling stage in Triticum aestivum (wheat) is highly vulnerable to increasing temperature as terminal heat stress diminishes grain quality and yield. To examine the mechanism of terminal heat tolerance, we performed the biochemical and gene expression analyses using two heat‐tolerant (WH730 and WH1218) and two heat‐sensitive (WH711 and WH157) wheat genotypes. We observed a significant increase in total soluble sugar (25%–47%), proline (7%–15%), and glycine betaine (GB) (22%–34%) contents in flag leaf, whereas a decrease in grain‐filling duration, 1000‐kernel weight (8%–25%), and grain yield per plant (11%–23%) was observed under the late‐sown compared to the timely sown. The maximum content of osmolytes, including total soluble sugar, proline, and GB, was observed in heat‐tolerant genotypes compared to heat‐sensitive genotypes. The expression of 10 heat‐responsive genes associated with heat shock proteins (sHsp‐1, Hsp17, and HsfA4), flavonoid biosynthesis (F3′‐1 and PAL), β‐glucan synthesis (CslF6 and CslH), and xyloglucan metabolism (XTH1, XTH2, and XTH5) was studied in flag leaf exposed to different heat treatments (34, 36, 38, and 40°C) at 15 days after anthesis by quantitative real‐time polymerase chain reaction. A significant increase in the relative fold expression of these genes with increasing temperature indicated their involvement in providing heat‐stress tolerance. The high differential expression of most of the genes in heat‐tolerant genotype “WH730” followed by “WH1218” indicates the high adaptability of these genotypes to heat stress compared to heat‐sensitive wheat genotypes. Based on the previous results, “WH730” performed better in terms of maximum osmolyte accumulation, grain yield, and gene expression under heat stress.

Investigating the impact of terminal heat stress on contrasting wheat cultivars: a comprehensive analysis of phenological, physiological, and biochemical traits

“…However, genotypic variation in proline synthesis could be observed under extended heat stress, as tolerant genotypes exhibited a moderate increase in proline levels under extended heat conditions as compared to sensitive genotypes. Since the protective role of proline in the stabilization of proteins and antioxidant enzymes, direct scavenging of ROS, the balance of intracellular redox homeostasis (e.g., NADP + /NADPH and GSH/GSSG ratio), and cellular signaling is well documented, the higher content of proline in tolerant wheat genotypes could have an impact on plant survival under heat stress conditions and also serve as a biochemical marker for the early screening of the genotypes ( Liang et al., 2013 ; Dikilitas et al., 2020 ; Zhang et al., 2022 ; Sihag et al., 2023 ). Many plants accumulate a number of compatible osmolytes such as proline and various sugars under drought, heat, salinity, flood, heavy metals, and cold stress conditions, and these osmolytes function as osmo-protectants in plant stress tolerance ( Gupta and Kaur, 2005 ; Chaudhary et al., 2020 ; Moukhtari et al., 2020 ; Khan et al., 2021b ; Chugh et al., 2022 ).…”

Abiotic Stress in Plants: Sustainability and Productivity

“…However, genotypic variation in proline synthesis could be observed under extended heat stress, as tolerant genotypes exhibited a moderate increase in proline levels under extended heat conditions as compared to sensitive genotypes. Since the protective role of proline in the stabilization of proteins and antioxidant enzymes, direct scavenging of ROS, the balance of intracellular redox homeostasis (e.g., NADP + /NADPH and GSH/ GSSG ratio), and cellular signaling is well documented, the higher content of proline in tolerant wheat genotypes could have an impact on plant survival under heat stress conditions and also serve as a biochemical marker for the early screening of the genotypes (Liang et al, 2013;Dikilitas et al, 2020;Zhang et al, 2022;Sihag et al, 2023). Many plants accumulate a number of compatible osmolytes such as proline and various sugars under drought, heat, salinity, flood, heavy metals, and cold stress conditions, and these osmolytes function as osmo-protectants in plant stress tolerance (Gupta and Kaur, 2005;Chaudhary et al, 2020;Moukhtari et al, 2020;Khan et al, 2021b;Chugh et al, 2022).…”

Exploring the genomics of abiotic stress tolerance and crop resilience to climate change

“…The discussion underscored the implication of heat stress-related trait phenotyping and elucidated key molecular mechanisms that aid in identifying novel sources for heat stress tolerance, offering opportunities to enhance heat tolerance in maize. Furthermore, in the exploration of terminal heat tolerance mechanisms in wheat, Sihag et al (2023) conducted biochemical and gene expression analyses using two heat-tolerant and two heat-sensitive genotypes. The analysis revealed a notable increase in total soluble sugar, proline, and glycine betaine contents in the flag leaf, alongside a reduction in grainfilling duration, 1000-kernel weight, and grain yield under heat stress.…”

“…Furthermore, in the exploration of terminal heat tolerance mechanisms in wheat, Sihag et al. (2023) conducted biochemical and gene expression analyses using two heat‐tolerant and two heat‐sensitive genotypes. The analysis revealed a notable increase in total soluble sugar, proline, and glycine betaine contents in the flag leaf, alongside a reduction in grain‐filling duration, 1000‐kernel weight, and grain yield under heat stress.…”