In living organisms, small heat shock proteins (sHSPs) are triggered in response to stress situations. This family of proteins is large in plants and, in the case of tomato (Solanum lycopersicum), 33 genes have been identified, most of them related to heat stress response and to the ripening process. Transcriptomic and proteomic studies have revealed complex patterns of expression for these genes. In this work, we investigate the coregulation of these genes by performing a computational analysis of their promoter architecture to find regulatory motifs known as heat shock elements (HSEs). We leverage the presence of sHSP members that originated from tandem duplication events and analyze the promoter architecture diversity of the whole sHSP family, focusing on the identification of HSEs. We performed a search for conserved genomic sequences in the promoter regions of the sHSPs of tomato, plus several other proteins (mainly HSPs) that are functionally related to heat stress situations or to ripening. Several computational analyses were performed to build multiple sequence motifs and identify transcription factor binding sites (TFBS) homologous to HSF1AE and HSF21 in Arabidopsis. We also investigated the expression and interaction of these proteins under two heat stress situations in whole tomato plants and in protoplast cells, both in the presence and in the absence of heat shock transcription factor A2 (HsfA2). The results of these analyses indicate that different sHSPs are up-regulated depending on the activation or repression of HsfA2, a key regulator of HSPs. Further, the analysis of protein-protein interaction between the sHSP protein family and other heat shock response proteins (Hsp70, Hsp90 and MBF1c) suggests that several sHSPs are mediating alternative stress response through a regulatory subnetwork that is not dependent on HsfA2. Overall, this study identifies two regulatory motifs (HSF1AE and HSF21) associated with the sHSP family in tomato which are considered genomic HSEs. The study also suggests that, despite the apparent redundancy of these proteins, which has been linked to gene duplication, tomato sHSPs showed different up-regulation and different interaction patterns when analyzed under different stress situations.

Classical Hodgkin lymphoma (cHL) cells overexpress heat-shock protein 90 (HSP90), an important intracellular signaling hub regulating cell survival, which is emerging as a promising therapeutic target. Here, we report the antitumor effect of celastrol, an anti-inflammatory compound and a recognized HSP90 inhibitor, in Hodgkin and Reed–Sternberg cell lines. Two disparate responses were recorded. In KM-H2 cells, celastrol inhibited cell proliferation, induced G0/G1 arrest, and triggered apoptosis through the activation of caspase-3/7. Conversely, L428 cells exhibited resistance to the compound. A proteomic screening identified a total of 262 differentially expressed proteins in sensitive KM-H2 cells and revealed that celastrol’s toxicity involved the suppression of the MAPK/ERK (extracellular signal regulated kinase/mitogen activated protein kinase) pathway. The apoptotic effects were preceded by a decrease in RAS (proto-oncogene protein Ras), p-ERK1/2 (phospho-extracellular signal-regulated Kinase-1/2), and c-Fos (proto-oncogene protein c-Fos) protein levels, as validated by immunoblot analysis. The L428 resistant cells exhibited a marked induction of HSP27 mRNA and protein after celastrol treatment. Our results provide the first evidence that celastrol has antitumor effects in cHL cells through the suppression of the MAPK/ERK pathway. Resistance to celastrol has rarely been described, and our results suggest that in cHL it may be mediated by the upregulation of HSP27. The antitumor properties of celastrol against cHL and whether the disparate responses observed in vitro have clinical correlates deserve further research.

The green alga Chlamydomonas reinhardtii is a valuable photosynthetic model for dissecting signal transduction pathways. In this work, we investigated the role of SnRK2.1 through analysis of a loss‑of‑function mutant and its connection to the growth regulator TOR kinase and the transcription factor PSR1. Disruption of SnRK2.1 resulted in sustained starch accumulation under nutrient‑replete conditions, accompanied by slight changes in lipid content and reduced chlorophyll levels, yet without compromising biomass production. The mutant showed altered cell cycle progression, consistent with misregulation of TOR signaling, as evidenced by reduced phosphorylation of S6K and deregulated expression of CDKB1 and CYCA1. Under P starvation, PSR1 expression was strongly induced in the mutant and SnRK2.1 transcripts decreased in the wt, suggesting reciprocal regulation between SnRK2.1 and PSR1. Proteomic analysis further supported these observations and provided additional mechanistic insights. Major changes occurred in proteins related to translation, ribosomal structure, and biogenesis and photosynthesis (downregulated), and DNA replication (upregulated). Notably, two kinases related to SnRK2.1 (Sac3 and A8IA26), were up‑regulated, consistent with cross‑regulation among SnRK family members. Taken together, these findings position SnRK2.1 as a multifunctional kinase at the crossroads of C metabolism, TOR signaling, and nutrient stress responses. We report the first empirical evidence of a functional SnRK-TOR connection in microalgae and propose a regulatory triad involving SnRK2.1, TOR, and PSR1. Beyond its physiological significance, the finding that the snrk2.1 mutant accumulates twice the starch of wt without impairing growth underscores its biotechnological potential for starch‑rich strain engineering.

The Hsp20 protein family, essential in heat stress responses across all organisms, is part of the heat shock protein (Hsp) superfamily, recognized for its conserved alpha-crystallin domain (ACD). Hsp20s are the smallest proteins in the superfamily and primarily assist in protein refolding during stress and developmental processes. We present an in silico characterization of the Hsp20 gene family in Chenopodium quinoa (2n = 4x = 36) using an integrative approach. Quinoa is well known for its global contributions to food production and tolerance to various abiotic stresses. We identified 69 CqHsp20 genes that exhibit a well-conserved evolutionary pattern, characterized by a balanced copy number distributed symmetrically across 19 homeologous pairs in both subgenomes (A and B), with localized expansions driven by tandem duplications on eight chromosomes. High sequence identity in contiguous gene pairs and Ka/Ks ratios consistently below 1 (0.14–0.84) mathematically demonstrate that strict purifying selection has maintained the structural and sequence integrity of these genes since the ancestral polyploidization event. The phylogenetic analysis grouped CqHsp20 into two main clusters, splitted into four sub-clusters based on peptides’ cellular localization, consistent with a characteristic gene structure and conserved motif analysis, which may reflect the evolutionary trajectory and functional specialization of the Hsp20 family in plants. The integration of transcriptomic data from published experiments enabled us to detect a cluster of putatively ubiquitously expressed CqHsp20, as well as other groups that showed differential responses across abiotic stress conditions. The pattern shows that more genes exhibit higher transcription abundance under drought and salinity than under heat, key adaptive traits underlying quinoa’s known ecological versatility. Some of these genes, which are undetectable or have low abundance under heat stress, encode organelle-targeting peptides, a phenomenon not reported in other model plant studies. Differential expression analysis revealed a highly transcribed sub-cluster where six out of seven of nuclear CqHsp20 genes were active in aerial tissue during initial heat stress, with a specific cohort of four genes (CQ025082, CQ031384, CQ041158, and CQ055373) maintaining significant upregulation ($|{log}_2\mathrm{Fold}\mathrm{Change}|\ge 1.0$, $\mathrm{padj}<0.05$) under prolonged and simultaneous shoot/root exposure. Varying expression within CqHsp20 homologous and paralogs supports the idea that gene duplication creates genomic diversity, facilitating adaptation to variable extreme environments. However, while theoretical and in silico analysis provide valuable insight into quinoa Hsp20 response, empirical data are essential to unequivocally understand how these gene expression variations affect quinoa response to abiotic stressors.

The Hsp20 protein family, recognized in all organisms for its chaperone activity in the heat-stress response, is part of the Heat Shock Protein (Hsp) superfamily, defined by a conserved alpha-crystallin domain (ACD). Hsp20s are the smallest proteins in the superfamily (mostly between 15 and 22 kDa) and assist in protein refolding during stress and developmental processes. In this study, we characterize the Hsp20 gene family in Chenopodium quinoa (2n = 4x = 36) using an integrative omic approach. C. quinoa is well known for its global contributions to food production and tolerance to various abiotic stresses. We identified 69 CqHsp20 genes distributed across the nine chromosomes of each subgenome (A and B), organized mainly into homologous pairs, with paralogs on eight chromosomes, likely from tandem duplications, suggesting a well-conserved evolutionary pattern within the species. The phylogenetic analysis grouped CqHsp20 proteins into two main clusters, split into four sub-clusters based on peptides’ cellular localization, consistent with a characteristic gene structure and conserved motif analysis. The integration of transcriptomic data from published experiments enabled us to detect a cluster of putatively ubiquitously expressed CqHsp20, as well as other groups that showed differential responses across abiotic stress conditions. The pattern shows more genes with transcriptional activity under drought and salinity than under heat, key adaptive traits underlying quinoa’s known ecological versatility. Some of these genes, with null or low transcriptional activity under heat stress, encode organelle-targeting peptides, a phenomenon not reported in other model plant studies. Varying expression within CqHsp20 homologous and paralogs supports the idea that gene duplication creates genomic diversity, facilitating adaptation to variable extreme environments. However, while theoretical and in silico analysis provide valuable insight into quinoa Hsp20 response, empirical data are essential to unequivocally understand how these gene expression variations affect quinoa response to abiotic stressors.