Abstract
Potamogeton malaianus (MAL) shows phenotypic plasticity and grows under both submerged and terrestrial conditions. In contrast, its allied species P. perfoliatus (PER) can survive only in water. From cultivation experiments, we found a significant difference in thermotolerance between them, especially PER lacked the ability to acclimate to high temperature.
Heat shock transcription factor HsfA2, the most strongly induced by heat stress among Hsf family, is required for basal and acquired thermotolerance in Arabidopsis. We attempted to isolate this gene from MAL and PER, and obtained two genes, namely HsfA2a and HsfA2b. By heat treatment, HsfA2a was strongly expressed in both plants, while HsfA2b was induced in MAL but not in PER. The lack of PER-HsfA2b expression may be due to mutations in heat shock element (HSE) and a long insertion in the promoter region. The RT-PCR analysis of HsfA2 and Hsp during long-term acclimation revealed that Potamogeton HsfA2s may be differentiated functionally: HsfA2a is involved in basal thermotolerance and HsfA2b is essential for acquired thermotolerance.
