Molecular profiling of PYL gene family in sugar beet (Beta vulgaris L.) and BvPYL2/3 involved in ABA accumulation confers enhanced resistance to CLS (Cercospora Leaf Spot)

<i>Cercospora leaf</i> sp<i>ot</i> (<i>CLS</i>), caused by <i>Cercospora beticola</i>, is a major threat to sugar beet (<i>Beta vulgaris L.</i>) production globally. While abscisic acid (ABA) signaling mediates plant defense responses, the specific roles of ABA receptors (<i>PYR/PYL/RCAR</i>) in sugar beet resistance to <i>CLS</i> remain unclear. In this study, <i>10 BvPYL</i> genes were identified from the sugar beet genome and functionally characterized. Transcriptome profiling showed that <i>BvPYL2</i> displayed a stable constitutive expression profile in resistant and susceptible lines during infection, in contrast to <i>BvPYL3</i>, whose expression was marked by a significant decrease over the disease progression. Subcellular localization analysis revealed that both <i>BvPYL2</i> and <i>BvPYL3</i> localize to the plasma membrane, cytoplasm, and nucleus. Yeast two-hybrid assays demonstrated that <i>BvPYL2</i> constitutively interacts with the negative regulator <i>BvPP2C37</i>, while <i>BvPYL3</i> forms an ABA-dependent complex with <i>BvPP2C37</i>. Physiological observations showed that resistant plants achieved ABA-mediated stomatal closure to restrict pathogen entry, whereas susceptible plants maintained prolonged stomatal opening, facilitating infection. These results reveal two distinct regulatory mechanisms: <i>BvPYL2</i> functions through constitutive interaction with <i>BvPP2C37</i>, and <i>BvPYL3</i> operates via ABA-dependent signaling, both contributing to stomatal immunity against <i>CLS</i>. This study elucidates novel ABA-mediated defense mechanisms in sugar beet and identifies <i>BvPYL2</i> and <i>BvPYL3</i> as promising targets for breeding <i>CLS</i>-resistant germplasm.