['Transcription factor HaDREB2 was identified in sunflower (Helianthus annuus L.) as a drought-responsive element-binding factor 2 (DREB2) with unique properties. HaDREB2 and the sunflower Heat Shock Factor A9 (HaHSFA9) co-activated the Hahsp17.6G1 promoter in sunflower embryos. Both factors could be involved in transcriptional co-activation of additional small heat stress protein (sHSP) promoters, and thus contribute to the HaHSFA9-mediated enhancement of longevity and basal thermotolerance of seeds.', 'We found that overexpression of HaDREB2 in seeds did not enhance longevity. This was deduced from assays of basal thermotolerance and controlled seed-deterioration, which were performed with transgenic tobacco. Furthermore, the constitutive overexpression of HaDREB2 did not increase thermotolerance in seedlings or result in the accumulation of HSPs at normal growth temperatures. In contrast, when HaDREB2 and HaHSFA9 were conjointly overexpressed in seeds, we observed positive effects on seed longevity, beyond those observed with overexpression of HaHSFA9 alone. Such additional effects are accompanied by a subtle enhancement of the accumulation of subsets of sHSPs belonging to the CI and CII cytosolic classes.'] Does the HaDREB2 transcription factor enhance basal thermotolerance and longevity of seeds through functional interaction with HaHSFA9?