Genome-wide identification and analysis of monolignol biosynthesis genes in Salix matsudana Koidz and their relationship to accelerated growth

Lignin plays an important role in plant growth and development. It serves as a raw material for the manufacture of paper, animal feed, and chemical fertilizers. However, the regulation of lignin biosynthesis genes and the composition of the relevant gene families remain unclear in many plant species. Here, we identified and characterized 11 families of monolignol biosynthesis genes in Salix matsudana Koidz. Based on phylogenetic analysis of lignin biosynthesis genes from nine angiosperm species (Arabidopsis thaliana, Oryza sativa, Zea mays, Solanum lycopersicum, S. suchowensis, S. purpurea, Populus euphratica, P. trichocarpa, and S. matsudana), the 11 gene families could be divided into two classes that differed in their apparent evolutionary history. We compared the distribution of lignin biosynthesis genes between the two sub-genomes (At and Bt) of S. matsudana and found that more duplicated genes were present in the Bt sub-genome. We analyzed RNA sequencing data from two parents of contrasting height and two of their F1 progeny, and detected 23 differentially expressed genes (DEGs) that may regulate accelerated growth. We analyzed the promoter regions of the lignin-related DEGs and identified several hormone-related (auxin, ethylene, and cytokinin) transcription factor binding sites. These results provide an important foundation for future studies on the molecular mechanisms and genetic regulation of lignin biosynthesis and its relationship to accelerated growth in forest trees.