Revealing the relationship between nitrogen use efficiency-related QTLs and carbon and nitrogen metabolism regulation in poplar

<strong>Supporting information</strong> <strong>Figure S1. </strong>KEGG functional annotation of QTL candidate genes. <strong>Figure S2.</strong> Correlation analysis of 60 transcriptome sample data. <strong>Figure S3.</strong> Expression confirmation using quantitative real-time PCR. <strong>(a)</strong> Fragments per kilobase of exon model per million mapped fragments of target genes.<strong> (b)</strong> Relative expression of target genes by qRT‒PCR. <strong>Figure S4.</strong> Analysis of nitrogen response DEGs of 10 clones under high- and low-nitrogen conditions. <strong>(a) </strong>Statistical analysis of up- and downregulated genes in 10 clones under high- and low-nitrogen conditions.<strong> (b) </strong>Functional enrichment analysis of KEGG for all DEGs of 10 clones under high- and low-nitrogen conditions. The colour scale represents the adjusted <em>P</em> value (padj). The high-nitrogen condition is represented by the letters A, and the low-nitrogen condition is represented by the letters B. <strong>Figure S5.</strong> Difference analysis of carbon and nitrogen metabolism of 10 clones under high- and low-nitrogen conditions. <strong>(a)</strong> Comparison of differences in total nitrogen, total carbon, and the carbon to nitrogen ratio in the xylem.<strong> (b)</strong> Comparison of differences in total nitrogen, total carbon, and the carbon to nitrogen ratio in the bark. S1 is ‘Danhong’. S2 is ‘Tongliao 1’. S3-S10 are F1 offspring. <strong>Figure S6.</strong> Difference analyses of cellulose, hemicellulose, and lignin contents in the xylems of 10 clones under high- and low-nitrogen conditions. <strong>Figure S7. </strong>Difference analysis of hydrolysed amino acid content in the bark of 10 clones under high- and low-nitrogen conditions. <strong>Figure S8. </strong>Difference analysis of hydrolysed amino acid content in the xylems of 10 clones under low- and high-nitrogen conditions. <strong>Figure S9. </strong>WGCNA of 10 clones under high- and low-nitrogen conditions. Queue selection of WGCNA. <strong>(a) </strong>WGCNA power value testing and determination. <strong>(b) </strong>Module hierarchical clustering tree of WGCNA. <strong>Table S1. </strong>The original data of ground diameter, plant height, and stem biomass of the hybrid population. The original data were averaged. <strong>Table S2. </strong>Summary of QTL mapping results for NUE-related traits. <strong>Table S3. </strong>Functional annotation of candidate genes for QTLs. <strong>Table S4.</strong> Summary of the RNA-Seq results. The high-nitrogen condition is represented by the letters A, and the low-nitrogen condition is represented by the letters B. <strong>Table S5.</strong> The primers used in this study.