Identification of heat shock-inducible transcripts and Hop (Hsp-organizing protein)-interacting proteins in orchardgrass (Dactylis glomerata L.)

Abstract

Plants are continuously exposed to temperature changes and biotic/abiotic stresses. Current global warming dynamics cause extreme temperature fluctuations that severely affect crop productivity. Orchardgrass (Dactylis glomerata L.) is one of the most important perennial grasses adapted for cool temperatures. Orchardgrass displays rapid establishment, vigorous growth, and rapid recovery after cutting or grazing, but it is sensitive to heat stress. In this study, we isolated 23 heat shock-inducible partial gene fragments from orchardgrass using a differential-display RT-PCR and a reverse northern blotting. Those full-length cDNAs encode major molecular chaperones (Hsp90s, Hsp70, and small Hsp) and Hsp90 co-chaperones (Hop, p23, and Aha) were identified from a heat-treated orchardgrass cDNA library and analyzed those expressions by northern blot analysis. In addition, we further characterized Hop, which plays as an important adapter that organizes the Hsp90 and Hsp70 complex in the Hsp90-associated heteromultimeric chaperone complex. Orchardgrass Hop (DgHop) transcript levels were enhanced by heat shock stress and dramatically reduced by cold, salt, or dehydration stress. DgHop contains three conserved tetratricopeptide repeat domains, which are involved in interactions with major Hsps. Yeast two-hybrid and pull-down analysis indicated that the major DgHop client proteins were Hsp90 and Hsp70, and DgHop directly interacted with DgHsp90 and DgHsp70. Our data provide new genetic information on heat shock responses in orchardgrass. We suggest that this information contribute to generating heat shock-tolerant forage crops.