Required for acclimation and survival during thermal stress. Heat-specific cofactor of XRN4 required for its targeting to polysomes and subsequent rapid degradation of seedling transcriptome during the early steps of the heat stress response. Interacts with XRN4 and facilitates its attachment to polysomes upon heat stress. Translocates from cytosol to P-bodies upon heat stress. Additional isoforms seem to exist. Reduced heat-induced fold reduction of mRNAs and impaired attachment of XNR4 to polysomes. Belongs to the LARP family.