MeSRT1 Interacts with MeNF-YC15 and Negatively Mediates Resistance to Cassava Bacterial Blight via Regulation of Gibberellin Metabolism in Manihot esculenta Crantz

Cassava (Manihot esculenta Crantz) has significant economic value as a vital source of food, feed, and bio-energy. However, the production of cassava is severely restricted by cassava bacterial blight (CBB). Sirtuins (SRTs) are conserved histone deacetylases that play essential roles in the plant energy metabolism and stress response. However, the family of SRTs has not been identified in cassava. In this study, we isolated and identified three MeSRTs in response to CBB infection and found that they were negative regulators of cassava resistance using a transient gene-silencing assay. Further studies found that MeSRT1 physically interacted with the transcription factor Nuclear Factor YC15 (MeNF-YC15). Transient silencing and overexpression assays suggested that MeSRT1 negatively regulated the transcription of gibberellin 2-oxidases 1/2 (MeGA2ox1/2), which promoted the accumulation of gibberellic acid 1 (GA1). However, MeNF-YC15 promoted the transcription of MeGA2ox1/2 and further increased the metabolism of GA1. Taken together, MeSRT1 and MeNF-YC15 antagonistically regulated the GA1 content and resulted in an antagonistic effect on cassava disease resistance. This study identified a MeSRT1-MeNF-YC15 molecular module in CBB resistance responses by regulating the GA1 content in cassava.