Heat shock proteins act as molecular chaperones that protect other proteins from aggregation and irreversible damage under environmental stress. Among them, Hsp20 proteins participate in plant growth, development, and responses to heat, cold, drought, and other adverse conditions. Members of the Euphorbiaceae originated mainly in tropical or subtropical regions but now occupy climates ranging from the tropics to temperate zones. Although Hsp20 gene families have been characterized in model plants and several crops, their genome-wide composition, evolutionary history, and contribution to temperature adaptation in Euphorbiaceae remained poorly understood. This knowledge gap has limited efforts to explain how these ecologically and economically valuable plants adjust to changing climates.
A study (DOI: 10.48130/tp-0026-0017) published in Tropical Plants on 12 June 2026 by Xiaohui Yu’s & Yinhua Chen’s team, Hainan University, reports that Hsp20 genes underwent extensive evolutionary diversification and identifies four candidates potentially associated with temperature adaptation.
The researchers examined genome sequences from cassava (Manihot esculenta), castor bean (Ricinus communis), physic nut (Jatropha curcas), rubber tree (Hevea brasiliensis), tung tree (Vernicia fordii), Mercurialis annua, and Euphorbia peplus. Using hidden Markov model and sequence-similarity searches, they identified proteins containing the conserved α-crystallin domain characteristic of Hsp20 proteins. The team then analyzed chromosomal positions, protein properties, conserved motifs, promoter regulatory elements, phylogenetic relationships, whole-genome duplication events, genomic collinearity, predicted protein interactions, and functional pathways. Cassava was selected as a representative species for transcriptomic analysis across different tissues and under drought and cold treatments. In total, the study identified 252 Hsp20 genes: 17 in E. peplus, 23 in castor bean, 24 in physic nut, 32 in M. annua, 50 each in cassava and rubber tree, and 56 in tung tree. Phylogenetic analysis grouped the proteins into 13 subfamilies, with most belonging to a cytoplasmic or nuclear group. All identified syntenic gene pairs were associated with segmental duplication and had experienced purifying selection, indicating that their functions were conserved during evolution. Twenty-four Hsp20 genes located in conserved genomic blocks may trace back to an ancient β whole-genome duplication event. Promoter analysis further showed that 207 of the 252 genes contained predicted binding sites for heat shock transcription factors. Cassava expression profiles suggested that at least 16 genes participate in tissue growth and development, while 25 responded to drought. By contrast, only two showed clear induction under cold stress, suggesting that many Euphorbiaceae Hsp20 genes may be more closely associated with adaptation to high temperatures than to cold. Comparative evidence highlighted MeHsp20-17, EpHsp20-7, MaHsp20-14, and HbHsp20-30 as candidate temperature-adaptation genes, although their precise functions require experimental validation.
Overall, the study provides the first broad comparative map of the Hsp20 family across representative Euphorbiaceae species. It connects gene-family expansion, evolutionary conservation, regulatory potential, and tissue- or stress-specific expression with the environmental adaptation of these plants. The results offer promising targets for functional studies using gene editing, overexpression, and physiological testing. Confirming how the identified genes influence heat tolerance could eventually assist molecular breeding and conservation, strengthening the resilience of major food, rubber, biofuel, medicinal, and industrial crops under climate change.
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References
DOI
10.48130/tp-0026-0017
Original Source URL
https://doi.org/10.48130/tp-0026-0017
Funding information
This work was supported by the National Natural Science Foundation of China (32260468) and the earmarked fund for the China Agriculture Research System (CARS-11-HNCYH).
About Tropical Plants
Tropical Plants (e-ISSN 2833-9851) is the official journal of Hainan University and published by Maximum Academic Press. Tropical Plants undergoes rigorous peer review and is published in open-access format to enable swift dissemination of research findings, facilitate exchange of academic knowledge and encourage academic discourse on innovative technologies and issues emerging in tropical plant research.