Abstract
Heat stress in plant results in repression of most mRNA translation and the preferential translation of heat shock protein mRNAs. The 5' untranslated region (5'UTR) of HSP mRNA is well known to confer the preferential translation during heat stress. In this study, we showed that the m7G-capped mRNA with 5'UTR of Arabidopsis heat shock protein (HSP81-3) gene was translated efficiently under heat stress condition by using Arabidopsis T87 protoplast transient expression assay. To investigate the function of HSP81-3 5'UTR in more detail, we performed the same transient expression assay using uncapped mRNA or dual luciferase assay vector for measuring IRES activity. As a result, HSP81-3 5'UTR conferred the temperature dependent increase of both translation efficiency of uncapped mRNAs and IRES activity. Thus, activation of the IRES activity depending on temperature may contribute the effective translation of HSP81-3 mRNA during heat stress which inhibits cap-dependent translation.
