Heat stress disrupts protein homeostasis, yet the thermoregulatory roles of HSP10/CPN10 co-chaperonins in polyploid crops remain unexplored. This study conducted the first genome-wide characterization of the HSP10 gene family in allotetraploid Brassica juncea to identify heat tolerance candidates. Genome-wide identification of BjuHSP10 genes was performed across A and B subgenomes, followed by phylogenetic, gene structure, duplication, synteny, promoter, and structural analyses. Transcriptional responses were evaluated under moderate (28/24 °C) and severe (36/32 °C) heat stress conditions. Ten BjuHSP10 genes were identified, encoding six mitochondrial, three chloroplast-targeted, and one cytoplasmic protein. Mitochondrial members were small (~10.7 kDa) with three-exon structures, whereas chloroplast members were larger (15.5–27.1 kDa) with complex exon–intron organization. Segmental duplication drove family expansion (19 duplicated pairs), with differential retention of Arabidopsis homologs. Promoter regions contained 391 putative cis-regulatory elements associated with stress, hormonal, and developmental regulation. Under heat stress, BjuHSP10-4 and BjuHSP10-5 were induced under both treatments; BjuHSP10-1/3/6/9 responded only to severe stress, while four genes were repressed. Structural modeling confirmed conserved β-rich GroES/CPN10-like folds. These findings identify candidate BjuHSP10 genes, particularly BjuHSP10-4 and BjuHSP10-5, as promising targets for heat-tolerance improvement in mustard, providing a foundation for future breeding and functional studies in polyploid crops.

The reproductive stage is a critical time in a plant’s life history when dealing with heat stress as the specific processes of meiosis, gametogenesis, anthesis, pollination, fertilization, and early seed development all occur within comparatively narrow temperature limits. Much of the importance of flowering is tied directly to temperature, both for the timing of reproductive transition and the ability for male and female reproductive tissues to survive exposure to damaging heat. Ambient-temperature sensing is linked to flowering via regulatory modules that involve phytochrome B, EARLY FLOWERING 3 (ELF3), PHYTOCHROME INTERACTING FACTOR 4 (PIF4), FLOWERING LOCUS T (FT), FLOWERING LOCUS M (FLM), SHORT VEGETATIVE PHASE (SVP), and the light–circadian components. Conversely, when temperature is harmful, protective responses involve other cellular mechanisms such as activation of heat-shock transcription factors (HSFs), heat-shock proteins (HSPs), endoplasmic-reticulum protein quality control, calcium and reactive oxygen species (ROS) signaling, antioxidant systems, hormone regulation, metabolic reprogramming, autophagy and DNA-repair pathways. Male reproductive development is often very sensitive, especially at meiosis, during formation of the tetrad, microspore development, during the maturation of pollen, and during the growth of the pollen tubes, although injury to pistils, ovules and the post-fertilization tissues may solely have an effect on the restriction of fertilization and seed set. Phenological heat escape and intrinsic reproductive thermotolerance are genetically separable but can be complementary aspects of adaptation, as revealed by natural allelic variation, QTL mapping, genomic prediction and marker assisted selection. This review summarizes molecular, genetic and physiological evidence, to propose that, to ensure stable yields at high temperatures, there is a need to coordinate optimization of reproductive timing, cell and development thermotolerance, and post-fertilization sink stability.

Background/Objectives: Dehydrins (DHNs) are late embryogenesis abundant proteins that play protective roles under water-deficit conditions; however, their organization and function remain unexplored in sesame (Sesamum indicum), an important oilseed crop frequently cultivated in arid and semi-arid regions. This study aimed to identify and characterize the DHN gene family in sesame and evaluate the expression of its members under drought stress. Methods: Genome-wide identification was performed using the Dehydrin domain HMM profile, followed by phylogenetic analysis, conserved motif and gene structure characterization, synteny analysis, promoter cis-element profiling, and secondary/tertiary structure prediction. Transcriptional responses were profiled by qPCR in two sesame cultivars (drought-sensitive and drought-tolerant) under PEG-induced osmotic stress at germination and seedling stages. Results: Four DHN genes were identified, spanning three phylogenetic subfamilies (I–III) and three DHN subclasses: SK_n (SiDHN1/2), Y_nK_n (SiDHN3), and Y_nSK_n (SiDHN4). SiDHN1 and SiDHN2 likely arose from a segmental duplication, and a single conserved syntenic pair was found between SiDHN4 and olive (Olea europaea). Secondary structure predictions uncovered contrasting structural propensities: SiDHN1/2 are predicted to be α-helix-rich, partially ordered proteins (41–44% predicted α-helix), whereas SiDHN3/4 are predicted to be predominantly intrinsically disordered (~75–80% random coil). SiDHN3 was consistently upregulated across all conditions (1.84–9.12-fold), while SiDHN4 exhibited strong genotype-specific induction of 9.39-fold exclusively in the drought-tolerant cultivar during germination. Conclusions: The sesame DHN family achieves functional breadth through structural diversification—an ordered–disordered continuum mirrored by divergent expression programming—rather than through numerical expansion. SiDHN3 and SiDHN4 are identified as primary candidates for drought tolerance improvement in sesame.