[Genome-wide identification and expression pattern analysis of Eucommia ulmoides Trihelix gene family]

Trihelix transcription factors play important roles in plant light responses, growth and development, and stress responses. However, Trihelix has not yet been reported in Eucommia ulmoides. In this study, bioinformatics methods were used to comprehensively identify and analyze the expression patterns of the Trihelix gene family in E. ulmoides, aiming to provide a basis for further functional studies of EuGTs genes. A total of 9 Trihelix gene family members were identified in E. ulmoides, encoding proteins with 339 to 883 amino acids, with isoelectric points ranging from 5.13 to 9.39 and relative molecular weights between 36 992.06 and 97 871.61. Subcellular localization results showed that only EuGT-2 was localized in chloroplasts, while the others were located in the nucleus. The Trihelix gene family was categorized into six subfamilies: GT-1, GT-2, SH4, SIP1, GTγ, and GTδ. EuGTs were distributed among three subfamilies: SH4, GT-1, and GT-2, containing 1, 6, and 2 Trihelix proteins, respectively, with 2 to 17 exons. The promoters of EuGTs contained various cis-acting elements related to hormones, stress, photoperiod, and growth and development. Collinearity analysis revealed 5 collinear gene pairs between E. ulmoides and Arabidopsis thaliana, and 14 collinear gene pairs between E. ulmoides and Populus. Expression pattern analysis showed that EuGTs exhibited tissue-specific expression: EuGT-1, EuGT-2 had the highest expression levels in leaves, EuGT-4, EuGT-6, EuGT-9 had the highest transcriptional levels in marginal peel, and EuGT-5、EuGT-8 were predominantly expressed in the xylem. As leaves developed, EuGTs showed a trend of asynchronous changes. No significant differences in EuGTs expression were observed between male and female flowers, with high expression levels mainly during the induction stage of flowering. The qRT-PCR analysis indicated that most EuGTs genes were most highly expressed in the leaves of E. ulmoides, while EuGT-5 was highly expressed in the stems. Under 200 mmol·L~(-1) NaCl treatment, most EuGTs genes exhibited an initial increase followed by a decrease in expression, significantly responding to salt stress. This study provides important genetic resources for further exploration of EuGTs gene functions and germplasm innovation in E. ulmoides.