Table 1

List of primer sequences"

Table 2

Analysis of the physicochemical properties of PfCCRs"

Fig.1

Phylogenetic relationships and gene structure of CCRs gene A: A phylogenetic tree is constructed using the neighbor-joining method with CCRs protein sequences from Paulownia, Arabidopsis thaliana, Zea mays, Triticum aestivum, Oryza sativa, Populus trichocarpa, resulting in five main branches. B: Conserved motif analysis of PfCCRs protein, showing 1–10 motifs, with each color representing a different motif. C: Conserved domain analysis of PfCCRs protein. D: Exon structure of PfBZRs, where CDS: Coding sequence, UTR: Untranslated region."

Fig.2

Protein structural analysis of PfCCRs and AtCCRs A: Secondary structure analysis of Paulownia fortunei PfCCRs proteins. B: Tertiary structure analysis of Paulownia fortunei PfCCRs and Arabidopsis AtCCRs proteins. AtCCR1 and AtCCR2 have been shown to regulate lignin biosynthesis."

Fig.3

Analysis of cis-acting elements in the PfCCRs gene A: The promoter sequences (2 000 bp) of 14 PfCCR genes are analyzed using PlantCARE software. Each color represents a different cis-regulatory element, totaling 15 elements. B: Distribution of PfCCRs genes among the 14 cis-regulatory elements; the numbers indicate the quantity of cis-acting elements. C: Distribution of different cis-acting motifs in the PfCCRs gene promoters; the numbers indicate the quantity of cis-acting motifs."

Fig.4

Chromosome distribution and collinearity analysis of the PfCCRs gene A: Chromosomal distribution of the PfCCRs gene in Paulownia fortunei. B: Phylogenetic analysis of Paulownia fortunei with Sesamum indicum and Mimulus guttatus. Gray lines represent collinear blocks in the S. indicum and M. guttatus genomes. Blue lines represent collinear gene pairs. C: Phylogenetic analysis of Paulownia fortunei with Arabidopsis thaliana and Populus trichocarpa. Gray lines represent collinear blocks in the A. thaliana and P. trichocarpa genomes. Blue lines represent collinear gene pairs. D: Phylogenetic analysis of Paulownia fortunei with Oryza sativa and Zea mays. Gray lines represent collinear blocks in the Oryza sativa and Zea mays genomes. Blue lines represent collinear gene pairs."

Fig.5

Tissue-specific expression patterns of PfCCRs gene The expression patterns of PfCCRs in different tissues of healthy Paulownia fortunei seedlings are analyzed using RT-qPCR, with Pfactin as the internal reference gene. R: Root; S: Stem; L: Leaf; B: Apical bud. Error bars represent the standard error of the mean of three biological replicates. Statistical significance is determined using a t-test (*: P<0.05, **: P<0.01, ***: P<0.001, ****: P<0.000 1)"

Fig.6

Expression pattern analysis of PfCCRs genes under biological stress The expression patterns of PfCCRs in healthy and PaWB-infected seedlings of Paulownia fortunei and Paulownia tomentosa are analyzed using RT-qPCR， with Pfactin as the internal reference gene. PF: Paulownia fortunei healthy seedlings; PFI: PaWB-infected seedlings of Paulownia fortunei; PT: Paulownia tomentosa healthy seedlings; PTI: PaWB-infected seedlings of Paulownia tomentosa. Error bars represent the standard error of the mean of three biological replicates. Statistical significance is determined using a t-test (*: P<0.05, **: P<0.01, ***: P< 0.001, ****: P< 0.000 1)."

Fig.7

Expression pattern analysis of PfCCRs genes under drought stress The expression patterns of PfCCRs under drought stress are analyzed using RT-qPCR. Pfactin is used as the internal reference gene， and CK serves as the control (relative expression level set to 1.0). CK: control group treated with an equal amount of water; 24 h: experimental group sampled 24 hours after spraying with 150 g·L−1 PEG 6000; 3 d: experimental group sampled 3 days after spraying with 150 g·L−1 PEG 6000; 7 d: experimental group sampled 7 days after spraying with 150 g·L−1 PEG 6000. Error bars represent the standard error of the mean of three biological replicates. Statistical significance is determined using a t-test (*: P<0.05, ** P<0.01, ***: P<0.001，****: P<0.000 1)."

Fig.8

Expression pattern analysis of PfCCRs genes under salt stress The expression patterns of PfCCRs under salt stress are analyzed using RT-qPCR. Pfactin is used as an internal reference gene， and CK serves as the control (relative expression level set to 1.0). CK: Control group treated with an equal amount of water; 24 h: Experimental group sampled 24 hours after spraying with 50 g·L−1 NaCl; 7 d: Experimental group sampled 7 days after spraying with 50 g·L−1 NaCl. Error bars represent the standard error of the mean of three biological replicates. Statistical significance is determined using a t-test (*: P<0.05, **: P<0.01, ***: P<0.001, ****: P<0.000 1)."