Genome-wide transcriptional analysis of 14-3-3 genes in Paulownia fortunei under abiotic and biotic stresses

The 14-3-3 proteins are evolutionarily conserved regulators in eukaryotes and play pivotal roles in plant stress responses and immunity. Paulownia is a fast‑growing tree valued for its high‑quality timber and diverse industrial applications, but it encounters multiple abiotic and biotic stresses, including drought, salinity, and phytoplasma‑induced witches’ broom disease. To better understand the molecular mechanisms underlying stress resilience in Paulownia fortunei, a comprehensive analysis of the 14-3-3 gene family was conducted.

Genome‑wide identification revealed 14 Paulownia fortunei (P. fortunei) general regulatory factor (PfGF) genes, which were phylogenetically classified into ε and non‑ε groups, each exhibiting distinct exon‑intron structures and stress‑responsive cis‑elements in their promoters. Transcriptome and quantitative real‑time PCR analyses demonstrated their differential expression under drought, salt, and phytoplasma infection. Notably, PfGF10 was upregulated under drought, PfGF2 showed salt‑specific induction, while PfGF7 was downregulated in phytoplasma‑infected axillary buds, suggesting its involvement in witches’ broom disease progression. Molecular docking, yeast two‑hybrid, and bimolecular fluorescence complementation assays confirmed that PfGF7 interacts with Paulownia fortunei receptor‑like kinase a (RLKa), receptor‑like kinase b (RLKb), and mitogen‑activated protein kinase kinase kinase A (MAPKKKA); similarly, PfGF11 interacts with the same three partners. Subcellular localization in Nicotiana benthamiana leaves revealed that PfGF7, PfGF11, PfRLKa, and PfRLKb localize to the cell membrane. Furthermore, co‑expression of PfGF7 or PfGF11 with PfRLKa, PfRLKb, or PfMAPKKKA in N. benthamiana leaves significantly induced cell death and upregulated the expression of defense genes including NbPR1a, NbLOX, and NbERF1.

Our findings suggest that Paulownia fortunei PfGF proteins modulate the MAPK signaling pathway, potentially regulating immune responses through their interactions with receptor‑like kinases and MAPKKKA. This study provides crucial insights for cultivating stress‑resistant Paulownia varieties and advancing sustainable forestry practices.