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.

TaAP2-10, an AP2/ERF transcription factor, contributes to wheat resistance against stripe rust.

The AP2/ERF TF (transcription factor) family is involved in regulating plant responses to various biotic and abiotic stresses. Nevertheless, understanding of the function of AP2/ERF TFs in wheat (Triticum aestivum L.) resistance against the obligate biotrophic stripe rust fungus (Puccinia striiformis f. sp tritici, Pst) remains limited. From a wheat-Pst incompatible interaction cDNA library, the transcript of TaAP2-10 was identified to be significantly induced during Pst infection. TaAP2-10, encodes an AP2 TF with two typical AP2-binding domains. There are three homologues of TaAP2-10 in the wheat genome, located on chromosome 6A, 6B and 6D. TaAP2-10 is localized in the nucleus of wheat protoplasts. A transactivation assay in yeast revealed that TaAP2-10 had transcriptional activation activity that was dependent on its C-terminal region. Quantitative real-time PCR (qRT-PCR) analyses verified that the expression of TaAP2-10 was specifically upregulated by avirulent Pst infection but not by virulent Pst, suggesting its role in wheat resistance to Pst. Furthermore, TaAP2-10 is also induced by abiotic stresses and hormone treatments, particularly under PEG4000 and abscisic acid (ABA) treatments, indicating its potential role in facilitating wheat adaptation to environmental stresses. Silencing TaAP2-10 by barley stripe mosaic virus-induced gene silencing (BSMV-VIGS) significantly reduced wheat resistance against Pst, resulting in a decreased reactive oxygen species (ROS) burst, and promoted Pst growth and development. These findings suggest that TaAP2-10, as a nuclear-localized transcription factor, positively regulates wheat resistance to Pst.