Essential protein required for basal thermotolerance, especially during heat-induced chromocentre decondensation, thus regulating transcriptional gene silencing (TGS). Localizes to the chromocentre at 23 degrees Celsius, a condensed heterochromatin domain that harbors repetitive elements for which transcription is normally suppressed by transcriptional gene silencing (TGS) (PubMed:23408827, PubMed:25329561). Relocates from the chromocenter to the nucleolus in response to heat (30 hours at 37 degrees Celsius or 30 minutes at 44 degrees Celsius), before heat-induced decondensation of chromocenters occurs (PubMed:25329561). Expressed predominately at the early stages during embryogenesis. Embryo lethal in homozygous plants. Hypersensitivity to heat leading to the inability to withstand prolonged heat stress (4 days at 37 degrees Celsius), probably due to impaired heat-induced chromocentre decondensation associated with attenuated heat reactivation of various transcriptional gene silencing (TGS) loci.