Glutathione S-transferases (GSTs) play a crucial role in responding to abiotic stress and are an important target for research on plant stress tolerance mechanisms. Populus euphratica is a promising candidate species for investigating the abiotic tolerance mechanisms in woody plants. In our previous study, PeGSTU58 was identified as being associated with seed salinity tolerance. In the present study, PeGSTU58 was cloned from P. euphratica and functionally characterized. PeGSTU58 encodes a Tau class GST and is located in both the cytoplasm and nucleus. Transgenic Arabidopsis overexpressing PeGSTU58 displayed enhanced tolerance to salt and drought stress. Under salt and drought stress, the transgenic plants exhibited significantly higher activities of antioxidant enzymes, including SOD, POD, CAT, and GST, compared to the wild-type (WT) plants. Additionally, the expression levels of several stress-responsive genes, including DREB2A, COR47, RD22, CYP8D11, and SOD1 were upregulated in PeGSTU58 overexpression lines compared to those in WT Arabidopsis under salt and drought stress conditions. Furthermore, yeast one-hybrid assays and luciferase analysis showed that PebHLH35 can directly bind to the promoter region of PeGSTU58 and activate its expression. These results indicated that PeGSTU58 was involved in salt and drought stress tolerances by maintaining ROS homeostasis, and its expression was positively regulated by PebHLH35.

Late embryonic developmental abundant (LEA) genes play a crucial role in the response to abiotic stress and are important target genes for research on plant stress tolerance mechanisms. Acer truncatum Bunge is a promising candidate tree species for investigating the tolerance mechanism of woody plants against abiotic stress. In our previous study, AtruLEA1 was identified as being associated with seed drought tolerance. In this study, LEA1 was cloned from A. truncatum Bunge and functionally characterized. AtruLEA1 encodes an LEA protein and is located in the nucleus. Phylogenetic tree analysis revealed a recent affinity of the AtruLEA1 protein to AT3G15760.1. Overexpression of AtruLEA1 resulted in enhanced tolerance of Arabidopsis thaliana to drought and salt stress and heightened the ABA sensitivity. Compared to wild-type (WT) plants, plants with overexpressed AtruLEA1 exhibited increased activities of antioxidant enzymes under drought stress. Meanwhile, the ROS level of transgenic Arabidopsis was significantly less than that of the WT. Additionally, the stoma density and stoma openness of AtruLEA1 Arabidopsis were higher compared to those in the WT Arabidopsis under salt and drought stress conditions, which ensures that the biomass and relative water content of transgenic Arabidopsis are significantly better than those of the WT. These results indicated that AtruLEA1 was involved in salt and drought stress tolerances by maintaining ROS homeostasis, and its expression was positively regulated by abiotic stress. These results indicate a positive role of AtruLEA1 in drought and salt stress and provide theoretical evidence in the direction of cultivating resistant plants.

Drought stress is one of the major environmental factors severely restricting plant development and productivity. Acer truncatum B, which is an economically important tree species, is highly tolerant to drought conditions, but the underlying molecular regulatory mechanisms remain relatively unknown. In this study, A. truncatum seedlings underwent a drought treatment (water withheld for 0, 3, 7, and 12 days), after which they were re-watered for 5 days. Physiological indices were measured and a transcriptome sequencing analysis was performed to reveal drought response-related regulatory mechanisms. In comparison to the control, the drought treatment caused a significant increase in antioxidant enzyme activities, with levels rising up to seven times, and relative electrical conductivity from 14.5% to 78.4%, but the relative water content decreased from 88.3% to 23.4%; these indices recovered somewhat after the 5-day re-watering period. The RNA sequencing analysis identified 9126 differentially expressed genes (DEGs), which were primarily involved with abscisic acid responses, and mitogen-activated protein kinase signaling. These DEGs included 483 (5.29%) transcription factor genes from 53 families, including ERF, MYB, and NAC. A co-expression network analysis was conducted and three important modules were analyzed to identify hub genes, one of which (AtruNAC36) was examined to clarify its function. The AtruNAC36 protein was localized to the nucleus and had a C-terminal transactivation domain. Moreover, it bounded specifically to the NACRS element. The overexpression of AtruNAC36 in Arabidopsis thaliana resulted in increased drought tolerance by enhancing antioxidant enzyme activities. These findings provide important insights into the transcriptional regulation mediating the A. truncatum response to drought. Furthermore, AtruNAC36 may be relevant for breeding forest trees resistant to drought stress.

Acer truncatum Bunge exhibits remarkable cold tolerance at the mature seedling stage, yet the mechanisms governing its seed germination under low-temperature conditions remain poorly understood. To elucidate the molecular and physiological mechanisms underlying low-temperature germination in A. truncatum seeds, we selected A. truncatum seeds as the experimental material. The seeds were evenly divided into two groups and subjected to germination under 25 °C (control) and 4 °C (low-temperature stress) conditions, followed by transcriptome sequencing and physiological and biochemical analyses. Transcriptome sequencing analyzed differential genes and physiological indicators. Fourteen transcription factor families were identified (ARR-B, AP2-EREBP, bHLH, NAC, FAR1, MADS, WRKY, AB13VP1, bZIP, C3H, CROS, LOB, TCP, and SBP). These regulate seed germination under abiotic/biotic stress. GO term enrichment occurred in biological processes. KEGG enrichment involved carbon metabolism, the glutathione pathway, the citrate cycle, and glycolysis. Most genes were upregulated. Citrate cycle and glycolysis correlated with seed activity, promoting germination. The glutathione cycle greatly improves the stress resistance of seed germination. There were 1804 genes that were upregulated and 8075 genes that were downregulated during seed germination. Among differential genes, CBF 5 was significantly downregulated but most WRKY families and LEA14-A were upregulated to maintain cell homeostasis. Meanwhile, GSH, SOD, POD, and proline (Pro) levels increased with prolonged stress. MDA rose initially, then declined. Soluble protein content first increased, then decreased, but remained higher than controls. Seeds germinated under low temperature, but germination potential was slightly lower than at room temperature. We propose that LEA protein, antioxidant enzymes, and Pro accumulation enhance cold tolerance. This study elucidates the physiological and molecular mechanisms underlying seed germination, advancing the understanding of cold tolerance in A. truncatum.