Overall, the results suggest that genotype-dependent responses to prolonged heat exposure were associated not only with the magnitude of early transcriptional change, but also with differences in the temporal organization of stress-response, maintenance, and metabolic processes.
Abstract
Heat stress is one of the most damaging abiotic constraints on crop productivity, and its consequences are expected to intensify as extreme temperature events become more frequent and severe. Pepper (Capsicum annuum L.) is particularly vulnerable to sustained high temperatures, which can disrupt photosynthetic performance, cellular homeostasis, and redox regulation. However, the physiological and transcriptional dynamics underlying genotype-dependent responses to prolonged heat exposure remain insufficiently understood. We combined repeated physiological measurements with time-course RNA sequencing to compare GPC003240, previously identified as a candidate heat-tolerant accession, with two non-elite accessions, GPC010350 and GPC014930, which are phenotypically divergent from each other, under 40/30 °C Day/night temperatures for up to six days. GPC010350 maintained comparatively stable photosystem II performance and higher stomatal conductance, whereas GPC014930 showed progressive photochemical impairment and lower conductance; GPC003240 displayed a distinct, moderately responsive profile. Transcriptomic responses showed partial functional convergence during the early phase of stress exposure but diverged markedly after six days. When gene expression at day 6 was compared with the pre-treatment baseline separately within each genotype, 4,436 differentially expressed genes were detected in GPC010350, compared with 680 in GPC003240 and only 78 in GPC014930. The late response of GPC010350 was associated with enrichment of RNA- and ribosome-related, biosynthetic, DNA-repair, and genome-maintenance functions. By contrast, GPC014930 showed negative enrichment of photosynthesis, plastid organization, redox homeostasis, and translation-related processes. Global co-expression analysis identified a time-decreasing photosynthesis-associated module (ME5) and two time-increasing modules, ME12 and ME19, that were enriched in genes contributing to the late GPC010350 response. Integration of differential expressions, module membership, and functional annotation highlighted a heat shock transcription factor (Caz03g27980), HSP101 (Caz03g07770), and a dual-specificity phosphatase (Caz05g20970) as candidates for further investigation. Overall, the results suggest that genotype-dependent responses to prolonged heat exposure were associated not only with the magnitude of early transcriptional change, but also with differences in the temporal organization of stress-response, maintenance, and metabolic processes. The contrasting responses of the non-elite accessions GPC010350 and GPC014930 further highlight the value of phenotypically diverse germplasm for uncovering mechanisms relevant to future heat-tolerance breeding.
Extreme heat events driven by global warming increasingly threaten the productivity of tomato (
Solanum lycopersicum
L.). While thermotolerance is often evaluated through individual physiological traits, resilience emerges from coordinated, multi-level regulation across growth dynamics and cellular stress responses. Here, we analyzed a diverse and contrasting panel of cultivated and wild tomato genotypes to resolve multidimensional stress-response strategies. Morphological, physiological, and biochemical traits were systematically quantified and integrated using the Stress Tolerance Index (STI), Membership Function Value (MFV), and correlation network analysis.
Heat exposure induced pronounced, genotype-dependent divergence in biomass retention, membrane stability, pigment integrity, osmotic adjustment, and antioxidant capacity. Sensitive accessions (e.g.,
S. chilense
PI 251313) exhibited severe growth suppression, chlorophyll loss, and elevated lipid peroxidation. In contrast, the commercial cultivar
S. lycopersicum
cv. İksir maintained biomass and structural stability, whereas the wild accession
S. pimpinellifolium
PI 365957 displayed enhanced antioxidant coordination and membrane protection.
Network analysis revealed a heat-induced shift from growth-centered regulation to a tightly interconnected stress-response module, with strong associations among proline, superoxide dismutase, and catalase. Multivariate integration consistently ranked
S. lycopersicum
cv. İksir and
S. pimpinellifolium
PI 365957 as the most thermotolerant genotypes at the vegetative stage under acute thermal stress (45 °C), highlighting complementary adaptive strategies across cultivated and wild backgrounds.
Collectively, these findings establish thermotolerance as an emergent systems property and identify wild relatives as valuable reservoirs of coordinated stress-adaptive traits for climate-resilient tomato breeding.
E. Şimşek, Kubra Yildiz, Sertan Çevik et al.· BMC Plant Biology· 0 citations
Assessing intraspecific variation in thermal stress tolerance is key to predicting plant responses and long-term persistence under climate change, yet its underlying sources and temporal dynamics remain poorly understood. Using a common garden experiment with four ecologically-relevant temperatures, we evaluated the sources and temporal dynamics of variation in temperature stress tolerance of 18 Lemna minor clonal lines from contrasting climates. Our results showed that past adaptation, physiological acclimation, and within-line variation jointly contributed to variation in performance. The study provides the first evidence of adaptive genetic differentiation in heat stress tolerance in this ecologically-widespread freshwater species, with lines from warmer regions showing higher growth under heat stress. However, these differences were transient and diminished under prolonged exposure. Experimental lines also showed acclimation over time, but these responses were strongly temperature-dependent and occurred only under sub-optimal conditions. Additionally, replicates from some lines exhibited divergent performance trajectories under sustained heat stress, suggesting the emergence of novel phenotypic variation, potentially mediated by epigenetic mechanisms. These results show that heat stress tolerance in L. minor arises from multiple interacting sources and is dynamically shaped by both selective history and immediate exposure time, suggesting a more nuanced, multi-layer understanding of variation in heat stress tolerance.
Mario Blanco‐Sánchez, S. Sultan, KJF. Verhoeven· bioRxiv· 0 citations
Chilo sacchariphagus is a destructive sugarcane borer worldwide, and frequent extreme high temperatures disrupt its field populations. Clarifying larval thermal response mechanisms provides theoretical support for pest risk prediction under climate warming. Previous work has illustrated moderate heat induces canonical HSP activation, but the molecular responses of this pest to 41 °C extreme heat remain unclear. As such, we conducted non-reference transcriptome sequencing and 11 physio-biochemical assays on fifth-instar larvae exposed to 41 °C for 12 h (26 °C as control) to characterize its thermal regulatory network. De novo assembly yielded a comprehensive transcriptome resource, and analysis of differentially expressed genes revealed enrichment in energy metabolism, ER protein processing, MAPK signaling and autophagy pathways. Core HSP70/40 transcripts were significantly down-regulated while HSP80 showed stable transcription, suggesting that 41 °C may exceed the heat-shock protective threshold and potentially trigger heat damage. qRT-PCR validation of seven core stress genes confirmed the RNA-seq trends. Catalase (CAT) activity increased significantly; however, none of the annotated catalase genes showed transcriptional changes, whereas elevated CarE and AchE activities also lacked corresponding transcriptional shifts, implying post-translational or alternative regulatory mechanisms. Our data showed coordinated transcriptional and physiological changes under extreme heat. These findings provide a basis for further investigation into how C. sacchariphagus may respond to extreme heat under climate warming scenarios.
Ji-Li Wei, Feng-Ying Wang, Yong-Lin Ma et al.· Insects· 0 citations
A hormone- and anthocyanin-centered framework is proposed for understanding the apparent negative association between salt/drought tolerance and thermotolerance in B. rapa and suggests that hormone-directed anthocyanin metabolism may contribute to the negative association between osmotic tolerance and thermotolerance.
Mei Zheng, Pei-Rong Li, Xiao-Yun Xin et al.· Frontiers in Plant Science· 0 citations
This study deepens the mechanistic understanding of cold tolerance in melon seedlings, confirms that flavonoids and GSH metabolites act as core components facilitating plant stress adaptation, and supplies valuable genetic and metabolic resources to accelerate the breeding of cold-tolerant melon varieties.
Jiaying Zhang, D. Ren, Keyan Zhang et al.· Plant physiology and biochem...· 0 citations
Freezing injury during winter is a critical abiotic stress that severely impacts the growth, development and, fruit quality of deciduous fruit trees. Cold tolerance can be induced through seasonal cold acclimation, which involves coordinated adjustments in tissue structure, physiology, and biochemistry driven by natural low-temperature, with distinct strategies across plant species. However, the cold-tolerant mechanisms of pear trees during cold acclimation remain poorly understood. Here, one-year-old branches of 10 pear cultivar germplasms were evaluated for cold tolerance based on the semi-lethal low temperature (LT50), with three biological replicates across two consecutive experimental years (2021-2022). LT50 values varied significantly among these materials, ranging from -42.43 ℃ to -32.59 ℃ and exhibited a highly significant negative correlation with field freezing injury indices (r = 0.86091, p < 0.0001). Subsequently, integrating anatomical structure observation, physiological index determination, metabolomics, and transcriptomics (with three biological replicates, each with three technical replicates for all omics and molecular experiments), we compared the low-temperature stress responses of cold-resistant 'Shanli' and cold-sensitive 'Hanhong', with statistical validation via one-way ANOVA, Duncan's multiple range test, Pearson's correlation analysis, and gray relational analysis. The results demonstrated that with decreasing temperature, the xylem ratio and lignin content in 'Shanli' branches increased markedly compared to 'Hanhong', and overwintering capability was correlated with branch lignin synthesis (r = -0.7783, p < 0.01). Cold acclimation enhanced lignin accumulation in 'Shanli' branches by increasing guaiacyl (G) and syringyl (S) units, associated with increased activities of key enzymes (shikimate hydroxycinnamoyl transferase (HCT), caffeoyl shikimate esterase (CSE), ferulate 5-hydroxylase (F5H), cinnamyl alcohol dehydrogenase (CAD), peroxidase (POD)) and critical intermediate metabolites (phenylalanine, ferulic acid, sinapic acid) in the phenylpropanoid pathway. Transcriptomic analysis identified 75 differentially expressed genes (DEGs) (|log2FoldChange|≥1 and FDR < 0.05) mapped to the phenylpropanoid pathway. Five potential key genes from the HCT, CSE, F5H, CAD and POD gene families, together with their co-expressed genes (such as ERF105-like) were identified as potentially associated with lignin content and composition modulationce in pear branches, providing novel insights into the regulatory network of lignin synthesis under natur under cold stress. Our findings reveal relationships between lignin synthesis pathways and cold toleranal low-temperature stress and candidate genes for cold-resistant pear breeding.
Ying Zhao, Xingkai Yan, Ming Lu et al.· BMC Plant Biology· 0 citations
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