Ethylene response factor 113 regulates the growth and development of poplar through the tryptophan-dependent auxin metabolism.

ERF transcription factors play a pivotal role in orchestrating plant growth and development processes. In this study, PagERF113 was isolated from the 84 K poplar (Populus alba × P. glandulosa) and its function was detected using molecular and genetic methods. Subcellular localization and trans-activation assays indicated that PagERF113 lacks transcriptional activation capability, residing in both the cell membrane and nucleus. Phenotypic analyses revealed that transgenic poplar lines overexpressing PagERF113 (OE) exhibited weedy growth compared to wild-type (WT), characterized by small leaves, curved stems, and numerous but short adventitious roots. Conversely, no significant differences were observed between the transgenic lines with RNA interference (RNAi) mediated suppression of PagERF113 and WT. Microscopic and histological assessments demonstrated structural modifications in the leaves of OE, showing densely arranged and thickened palisade and spongy tissues. In the stem, there were discernible changes such as a reduction in the widths of the pith and xylem, a shortening of fiber lengths, a decrease in the area of fiber cells, a thinning of the secondary cell walls, and a decline in vessel density. Transcriptomics and metabolomics correlation analysis identified tryptophan metabolism was one of the key pathways that PagERF113 regulated. Subsequently, DAP-seq and Y1H (Yeast-One-Hybrid) analyses confirmed that the auxin-related gene PagGH3.6 is a target of PagERF113. LUC (dual-luciferase) assay further demonstrated that PagERF113 directly activates the expression of PagGH3.6. Collectively, these findings suggested that PagERF113 acts as a negative regulator of poplar growth by modulating the expression of PagGH3.6 in the tryptophan-dependent auxin synthesis pathway.