Ecotypic variation in chloroplast small heat-shock proteins and related thermotolerance in Chenopodium album

► Four novel genes encoding Cp-sHSPs were isolated with their promoters. ► Ecotypic variations in chloroplast small heat-shock proteins expression are indicative of associated thermotolerance. ► Differences in promoters, Cp-sHSPs transcription at gene and protein levels, related to thermotolerance rather than mature-protein sequences. ► Promoter analysis revealed significant variations in heat-shock elements and other core motifs.