Dissociation of transcription factor MYB94 and histone deacetylases HDA907/908 alleviates oxidative damage in poplar

Drought is one of the major threats to forest productivity. Oxidation stress is common in drought-stressed plants, and plants need to maintain normal life activities through complex reactive oxygen scavenging mechanisms. However, the molecular links between epigenetics, oxidation stress, and drought in poplar (Populus) remain poorly understood. Here, we found that Populus plants overexpressing PtrMYB94, which encodes an R2R3-MYB transcription factor that regulates the abscisic acid signaling pathway, displayed increased tolerance to extreme drought stress via upregulation of embryogenic cell phosphoprotein 44 (PtrECPP44) expression. Further investigation revealed that PtrMYB94 could recruit the histone deacetylases PtrHDA907/908 to the promoter of PtrECPP44 and decrease acetylation at lysine residues 9, 14, and 27 of histone H3, leading to relatively low transcriptional expression levels under normal conditions. Drought induced the expression of PtrMYB94 while preventing interaction of PtrMYB94 with PtrHDA907/908, which relaxed the chromatin structure and facilitated the binding of RNA polymerase II to the PtrECPP44 promoter. The upregulation of PtrECPP44 helped poplar alleviate oxidative damage and maintain normal cell activities. This study establishes a PtrMYB94-PtrECPP44 transcriptional regulatory module modified by PtrHDA907/908 in modulating drought-induced oxidative stress recovery. Therefore, our study reveals an oxidative regulatory mechanism in response to drought stress and provides insights into molecular breeding for stress resistance in poplar.