Comprehensive Genomic Analysis of Trihelix Transcription Factor Genes and Their Expression Underlying Abiotic Stress in Euphrates Poplar (Populus euphratica)

Trihelix transcription factors (TTFs) are light-sensitive proteins characterized by a triple-helix structure that play a crucial role in regulating plant growth and development, especially in response to abiotic stressors, such as drought and salinity. This intriguing family of proteins has been the focus of extensive functional studies across various plant species. Despite their recognized significance, the trihelix family in Populus euphratica has not been thoroughly explored, warranting more attention. This study identifies 35 full-length trihelix genes in Populus euphratica, which are grouped into five categories (GT-1, GT-gamma, GT-2, SIP1, and SH4) based on their conserved motifs and structural similarities, and these genes are unevenly distributed across 19 linkage groups on the chromosomes. A syntenic analysis was conducted in P. euphratica, comparing it to various other species. The promoters of P. euphratica contain numerous stress-responsive cis-elements, indicating the potential for these trihelix genes to respond to abiotic stress. RT-qPCR analysis discovered significant induction of the trihelix gene family in response to drought and salt stress, with 21 PeuTTF genes exhibiting distinct expression levels under drought conditions and five PeuTTF genes responsive to salt stress. Notably, heightened expression of PeuTTF6, PeuTTF9, and PeuTTF20 was observed in both roots and leaves during drought stress, suggesting that TTF expression is connected to the plant's response to such conditions. Additionally, significant increases in expression were noted for PeuTTF2, PeuTTF31, and PeuTTF32, which may be convoluted in the response to salt stress. These discoveries highlight the role that PeuTTF genes play in improving drought tolerance in P. euphratica plants. We offer new perspectives on the evolutionary trends and variants of PeuTTF genes in P. euphratica, and we establish the groundwork for understanding the functional properties of PeuTTF genes under salt-stressed and drought-stressed conditions. This study provides opportunities for the advancement of desert poplar agriculture and may have wider ramifications for tree plant breeding techniques targeted at improving tree performance and durability, particularly in dry areas.