Mediates both basal and acquired thermotolerance. Involved in the mechanisms necessary for quick response to heat and subsequent heritable transgenerational memory of heat acclimation (global warming) such as early flowering and attenuated immunity; this process includes epigenetic regulation as well as post-transcriptional gene silencing (PTGS) (PubMed:30778176). In response to heat, HSFA2 is activated and promotes the expression of REF6 which in turn derepresses HSFA2, thus establishing an heritable feedback loop able to trigger SGIP1 and subsequent SGIP1-mediated SGS3 degradation; this prevents the biosynthesis of trans-acting siRNA (tasiRNA) and leads to the release of HTT5, which drives early flowering but attenuates immunity (PubMed:30778176). Expressed in seedlings, leaves, stems, inflorescences and siliques. Target of TAS1 (trans-acting siRNA precursor 1)-derived small interfering RNAs in response to temperature variations. Up-regulated by cold (at 4 degrees Celsius) (PubMed:20622450). Highly up-regulated in seedlings exposed to heat shock (PubMed:24728648). Belongs to the heat induced plant HTT protein family.