Acts as subunit of the RNA polymerase II elongator complex, which is a histone acetyltransferase component of the RNA polymerase II (Pol II) holoenzyme and is involved in transcriptional elongation (By similarity). Promotes organs development by modulating cell division rate. Prevents abscisic acid (ABA) signaling leading to stomatal closure and seedling growth inhibition. Involved in oxidative stress signaling. Prevents anthocyanins accumulation. Accelerator of defense gene induction required for rapid defense gene induction, and for the establishment of both basal and effector-triggered immunity (ETI), in a NPR1-independent manner, but is not required for systemic acquired resistance (SAR) establishment.