A gene called NtHHL5 has been identified as a negative regulator of cold tolerance in tobacco (Nicotiana tabacum), according to a study published on 28 October 2026 in the journal Chemical and Biological Technologies in Agriculture. Rather than helping the plant withstand low temperatures, the protein encoded by this gene appears to work against cold defense, and silencing it produces plants that cope better with chilling conditions.
NtHHL5 belongs to the 3-hydroxyisobutyryl-CoA hydrolase-like protein family, whose biological functions in plants have remained largely unexplored, particularly in stress responses. Phylogenetic analysis showed that the tobacco gene is closely related to homologs from other solanaceous species and carries a conserved ECH_2 domain involved in fatty acid metabolism. The researchers note that cold stress is a major abiotic constraint that severely impairs tobacco growth and productivity, which motivated the investigation of this gene’s role.
Expression profiling revealed that NtHHL5 is preferentially expressed in trichomes, the hair-like structures on the plant surface, and is strongly induced by low temperature. Subcellular localization experiments using an NtHHL5-GFP fusion protein showed that the protein targets both the nucleus and the endoplasmic reticulum, positions consistent with a role in lipid-related processes.
To probe the gene’s function, the team created RNA interference lines in which NtHHL5 was silenced. Lipidomic analysis of these lines revealed significant remodeling of the leaf lipidome, with elevated levels of specific galactolipids, phospholipids, and lysophospholipids, as well as increased unsaturation of multiple lipid classes.
The phenotypic consequences were striking. Under cold stress, the NtHHL5 RNAi lines exhibited superior cold tolerance compared with wild-type plants. Measurements of stress markers showed reduced accumulation of reactive oxygen species, lower malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents, and higher activities of the antioxidant enzymes POD, SOD, and CAT in the silenced lines.
The study also examined molecular signaling downstream of the silencing. NtHHL5 silencing upregulated key cold-responsive genes, including NtICE1, NtCBF1-2, and NtCOR413, under cold stress.
Taken together, the authors conclude that NtHHL5 negatively modulates cold defense by three mechanisms: disrupting membrane lipid homeostasis, compromising antioxidant defense systems, and suppressing CBF signaling. In other words, when the gene is active, it appears to leave tobacco plants less prepared for cold on multiple fronts simultaneously.
The study identifies NtHHL5 as a promising genetic target for improving cold tolerance in tobacco and potentially other crops. Because the gene is strongly induced by low temperature yet acts against tolerance, manipulating its expression could offer a route to breeding varieties that maintain membrane stability and antioxidant capacity under chilling conditions. The findings were reported in a peer-reviewed, open-access article, and the version shared at publication is subject to further editorial edits before the final Version of Record.
Further work would be needed to confirm whether the same regulatory relationship holds in other solanaceous crops or under field conditions. Nevertheless, the combination of lipidomic, phenotypic, and gene-expression evidence provides a coherent picture of how a previously little-studied hydrolase-like protein shapes a crop’s response to one of agriculture’s most widespread abiotic stresses.
Subject of Research: The role of the NtHHL5 gene in lipid metabolism and cold stress tolerance in tobacco
Article Title: NtHHL5 modulates lipid metabolism and negatively regulates cold tolerance in Nicotiana tabacum
Article References: Gao, Z., Guo, X., Zhang, W., Zhang, L., Wei, X., Zhang, J., Xu, B., Zhang, H., Wang, X., Zhou, H., Xu, G., & Zhai, N. (2026). NtHHL5 modulates lipid metabolism and negatively regulates cold tolerance in Nicotiana tabacum. Chemical and Biological Technologies in Agriculture. https://doi.org/10.1186/s40538-026-01132-6
Image Credits: AI Generated
DOI: 10.1186/s40538-026-01132-6
Keywords: NtHHL5, Nicotiana tabacum, cold tolerance, lipid metabolism, RNA interference, membrane lipids, CBF signaling, antioxidant enzymes, reactive oxygen species, galactolipids, endoplasmic reticulum, plant stress
News Source: Juliet Wilcox. (October 28, 2026). Tobacco Gene NtHHL5 Acts as a Brake on Cold Tolerance by Reshaping Membrane Lipids. Scienmag.
