Completely dephosphorylates 'Ser-2', and partially 'Ser-5' and 'Ser-7' of the heptad repeats YSPTSPS in the C-terminal domain (CTD) of the largest RNA polymerase II subunit (RPB1). Involved in defense response. Acts as a negative regulator of immune gene expression and immunity to pathogen infections. Preferentially dephosphorylates 'Ser-2' of RNA polymerase II CTD. This counterregulates the MAP kinase (MAPK) or cyclin-dependent kinase C (CDKC)-mediated phosphorylation of CTD in response to pathogens and upon perception of microbe-associated molecular patterns (MAMPs). MAPKs phosphorylate and activate CDKCs, which are CTD kinases that positively regulate plant innate immunity. Acts as a negative regulator of stress gene transcription involved in abscisic acid (ABA) mediated signaling pathway and cold resistance. Acts as a post-transcriptional gene silencing (PTGS) suppressor