The SQUAMOSA promoter binding protein-like (SPL)SPL family genes play an important role in regulating plant growth and development, synthesis of secondary metabolites, and resistance to stress. Understanding of the role of the SPL family in tobacco is still limited. In this study, 42 NtSPL genes were identified from the genome of the tobacco variety TN90. According to the results of the conserved motif and phylogenetic tree, the NtSPL genes were divided into eight subgroups, and the genes in the same subgroup showed similar gene structures and conserved domains. The cis-acting element analysis of the NtSPL promoters showed that the NtSPL genes were regulated by plant hormones and stresses. Twenty-eight of the 42 NtSPL genes can be targeted by miR156. Transcriptome data and qPCR results indicated that the expression pattern of miR156-targeted NtSPL genes was usually tissue specific. The expression level of miR156 in tobacco was induced by Cd stress, and the expression pattern of NtSPL4a showed a significant negative correlation with that of miR156. These results suggest that miR156-NtSPL4a may mediate the tobacco response to Cd stress. This study lays a foundation for further research on the function of the NtSPL gene and provides new insights into the involvement of NtSPL genes in the plant response to heavy metal stress.

Cadmium (Cd)-induced oxidative stress detrimentally affects hyperaccumulator growth, thereby diminishing the efficacy of phytoremediation technology aimed at Cd pollution abatement. In the domain of plant antioxidant mechanisms, the role of glutathione peroxidase (GPX) in conferring Cd tolerance to tobacco (Nicotiana tabacum) remained unclear. Our investigation employed genome-wide analysis to identify 14 NtGPX genes in tobacco, revealing their organization into seven subgroups characterized by analogous conserved domain patterns. Notably, qPCR analysis highlighted NtGPX8a as markedly responsive to Cd²⁺ stress. Subsequent exploration through yeast two-hybridization unveiled NtGPX8a’s utilization of thioredoxins AtTrxZ and AtTrxm2 as electron donors, and without interaction with AtTrx5. Introduction of NtGPX8a into Escherichia coli significantly ameliorated Cd-induced adverse effects on bacterial growth. Transgenic tobacco overexpressing NtGPX8a demonstrated significantly augmented activities of GPX, SOD, POD, and CAT under Cd²⁺ stress compared to the wild type (WT). Conversely, these transgenic plants exhibited markedly reduced levels of MDA, H₂O₂, and proline. Intriguingly, the expression of NtGPX8a in both E. coli and transgenic tobacco led to increased Cd accumulation, confirming its dual role in enhancing Cd tolerance and accumulation. Consequently, NtGPX8a emerges as a promising candidate gene for engineering transgenic hyperaccumulators endowed with robust tolerance for Cd-contaminated phytoremediation.

Background: Hydroxycinnamoyl-CoA quinate hydroxycinnamoyl-transferase (HQT) is an essential enzyme for chlorogenic acid (CGA) biosynthesis in plants. Multiple HQT-encoding genes potentially involved in CGA synthesis in sweet potato (Ipomoea batatas) have been predicted. However, the functions of these genes have not been verified. Methods: In this study, the gene IbHQT1 was isolated from the sweet potato cultivar ‘Nanshu-88’ and functionally characterized using transgenic technology. Results: IbHQT1 encodes a protein comprising 431 amino acids, with conserved HXXXD and DFGWG motifs characteristic of BAHD acyltransferase family members. A phylogenetic analysis indicated that IbHQT1 has a close evolutionary relationship with StHQT in Solanum tuberosum. According to qPCR data, IbHQT1 is highly expressed in young leaves, and its expression is affected by exogenous MeJA (100 µM), ABA (100 µM), GA₃ (50 µM), and SA (100 µM). Analyses of cis-acting regulatory elements indicated that the IbHQT1 promoter contains multiple elements responsive to MeJA, ABA, SA, GA₃, and light. In plants overexpressing IbHQT1, CGA contents in mature leaves and storage roots increased 1.30- to 1.44-fold and 1.28- to 1.43-fold, respectively. Conversely, in IbHQT1-RNAi lines, CGA contents in mature leaves and storage roots decreased by 16–38% and 18–40%, respectively. Conclusions: These findings indicate that IbHQT1 positively regulates CGA biosynthesis in sweet potato plants.