关键词: 白花泡桐, CCR基因家族, 全基因组鉴定, 木质素, 逆境响应, 调控机制

Abstract:

Objective: To elucidate the genomic characteristics and functional divergence of cinnamoyl-CoA reductase (CCR), a key rate-limiting enzyme in the lignin biosynthetic pathway of Paulownia fortunei, the genome-wide identification and systematic analysis of the CCR gene family were conducted based on the whole-genome data. The lignin synthesis in P. fortunei and the response mechanisms to biotic and abiotic stresses were explored, which would provide a theoretical basis for the targeted breeding of new elite stress-resistant Paulownia varieties via genome editing technology. Method: The known CCR amino acid sequence from Arabidopsis thaliana was used as a query, with which BLAST alignment was performed against the P. fortunei genome database to obtain P. fortunei PfCCRs family members. Bioinformatics techniques were then used to analyze the evolutionary relationships, promoter binding elements, and collinearity of these family members. Real-time quantitative PCR (RT-qPCR) was employed to analyze the expression levels of P. fortunei PfCCRs in different tissues and under abiotic stress conditions. Result: 1) In this study, a total of 14 PfCCR members were identified in the P. fortunei genome, with amino acid lengths ranging from 111 to 360 aa. These members were classified into five subfamilies (Cluster Ⅰ to Cluster Ⅴ) and all contained the NADB_Rossmann domain. 2) The PfCCR promoter regions were enriched with cis-acting elements associated with light response, hormone signal response, and stress response. Furthermore, the PfCCR genes were unevenly distributed across 8 chromosomes, and 10 collinear gene pairs were identified between P. fortunei and the dicotyledonous plants Sesamum indicum (sesame) and A. thaliana CCRs. 3) Phylogenetic tree construction and analysis indicated that PfCCR9 and PfCCR11 clustered together with A. thaliana lignin synthesis regulator AtCCR1 and disease resistance-related gene AtCCR2 in Cluster Ⅰ. Furthermore, the expression of PfCCR9 and PfCCR11 was significantly upregulated under drought and salt stress, suggesting their critical roles in the molecular regulation of stress tolerance. In contrast, PfCCR12 expression was significantly upregulated in seedlings infected with Paulownia witches’ broom phytoplasma (PaWB), indicating an important function in pathogen stress response. 4) PfCCR1, PfCCR3, PfCCR6, PfCCR7, PfCCR11, PfCCR13, and PfCCR14 exhibited significantly high expression in stems, while PfCCR10 and PfCCR11 were highly expressed in roots, indicating that these 8 genes play important roles in lignin biosynthesis. Conclusion: This study has identified key members of the PfCCRs family that play a role in regulating lignin synthesis and stress resistance in Paulownia wood. Based on evolutionary analysis and expression level validation, PfCCR9 and PfCCR11 in Cluster Ⅰ, as well as PfCCR12 in Cluster Ⅰ, play important regulatory roles in stress resistance, making them candidate genes for breeding new stress-resistant Paulownia varieties.

Key words: Paulownia fortunei, CCR gene family, genome-wide identification, lignin, stress response, regulatory mechanisms