Genome-wide identification of the TCP transcription factors family and its response to abiotic stress in tobacco (Nicotiana tabacum L.)

TCP transcription factors are unique key transcriptional regulators exclusive to plants, playing an indispensable role in plant growth and development. In recent years, numerous studies have gradually unveiled the involvement of certain TCP transcription factors in abiotic stress responses, shedding light on the potential pivotal roles TCP family might play in plants’ reactions to abiotic stress. Although tobacco ( Nicotiana tabacum L.) is widely recognized as a model plant with economic significance, research into its TCP transcription factors concerning abiotic stress responses is still in its infancy. In this study, we identified 28 TCP transcription factors in the tobacco genome, designated NtTCP1 through NtTCP28. Phylogenetic analysis classified these genes into Class I (13 members) and Class II (15 members), all containing the conserved bHLH domain. Gene structure analysis revealed that tobacco TCP genes are structurally concise, with exon numbers ranging from 1 to 4. Cis-regulatory element analysis identified three types of elements in the promoter regions of NtTCP genes: plant hormone response, plant growth and development, and stress-related elements. Homology analysis revealed seven pairs of highly similar gene pairs in the tobacco TCP family, all resulting from segmental duplication. Subcellular localization experiments confirmed that four candidate genes ( NtTCP1/24/27/16 ) encode nuclear-localized proteins, and transcriptional self-activation assay revealed that only NtTCP24 exhibits self-activation capability. qPCR-based expression profiling under ABA, salt, osmotic, and cold stresses identified NtTCP16 as a candidate regulator of abiotic stress responses. Functional analysis demonstrated that NtTCP16 positively regulates cold tolerance in tobacco. Under low-temperature stress, NtTCP16-overexpressing lines exhibited significantly increased activities of SOD, POD, and CAT, along with elevated proline and soluble sugar accumulation and reduced MDA content, indicating enhanced antioxidant capacity, osmotic adjustment, and membrane integrity. Collectively, these findings establish NtTCP16 as a positive regulator of cold stress tolerance in tobacco, acting through the modulation of multiple physiological defense pathways. This study provides preliminary information for the classification and functional analysis of the NtTCP gene family in tobacco, which may serve as a reference for future functional studies.