Genome-Wide Characterization of Berberine Bridge Enzyme Gene Family in Wheat (Triticum aestivum L.) and the Positive Regulatory Role of TaBBE64 in Response to Wheat Stripe Rust

Berberine bridge enzymes (BBEs), functioning as carbonate
oxidases,
enhance disease resistance in Arabidopsis and tobacco. However, the understanding of BBEs’ role in
monocots against pathogens remains limited. This study identified
81 TaBBEs with FAD_binding_4 and BBE domains. Phylogenetic analysis
revealed a separation of the BBE gene family between monocots and
dicots. Notably, RNA-seq showed TaBBE64’s
significant induction by both pathogen-associated molecular pattern
treatment and Puccinia striiformis f.
sp. tritici (Pst) infection at early
stages. Subcellular localization revealed TaBBE64 at the cytoplasmic
membrane. Knocking down TaBBE64 compromised wheat’s Pst resistance, reducing reactive oxygen species and promoting
fungal growth, confirming its positive role. Molecular docking and
enzyme activity assays confirmed TaBBE64’s glucose oxidation
to produce H2O2. Since Pst relies
on living wheat cells for carbohydrate absorption, TaBBE64’s
promotion of glucose oxidation limits fungal growth and resists pathogen
infection. This study sheds light on BBEs’ role in wheat resistance
against biotrophic fungi.