Sedum alfredii Hance, a cadmium (Cd)/zinc (Zn)/lead (Pb) co-hyperaccumulating species, is a promising phytoremediation candidate because it accumulates substantial amounts of heavy metal ions without showing any obvious signs of poisoning. The heat shock transcription factor (Hsf) family plays crucial roles in plant growth, development, and stress responses. Although the roles of some Hsfs in abiotic stress have been well studied in model plants, the Hsf family has not been systematically investigated in heavy metal hyperaccumulators. Here, we comprehensively analyzed the Hsf gene family in S. alfredii based on a transcriptome under Cd stress. There were 22 Hsf members that were identified and phylogenetically clustered into three classes, namely, SaHsfA, SaHsfB, and SaHsfC. All of the three classes shared similar motifs. The expression profiles of the 22 Hsf members showed significant differences: 18 SaHsfs were responsive to Cd stress, as were multiple SaHsp genes, including SaHsp18.1, SaHsp22, SaHsp26.5, SaHsp70, SaHsp90, and SaHsp101. Two class A4 members, SaHsfA4a and SaHsfA4c, exhibited transcriptional activation activities. Overexpression of SaHsfA4a and SaHsfA4c in transgenic yeast indicated an improved tolerance to Cd stress and Cd accumulation. Our results suggest SaHsfs play important regulatory roles in heavy metal stress responses, and provide a reference for further studies on the mechanism of heavy metal stress regulation by SaHsfs.

Hydrangea (Hydrangea macrophylla), a globally significant ornamental species, suffers severe economic losses from leaf spot disease caused by Corynespora cassiicola. Through detached-leaf assays screening 40 commercial cultivars, this study identified seven resistant cultivars (‘Rivet’, ‘White Angel’, ‘Blue Danube’, ‘Flora’, ‘Fire Works’, ‘Spring Bird’, and ‘Inspiration’) with distinct phenotypic clustering. Comparative analysis of resistant ‘White Angel’ (WA) versus susceptible ‘Ocean Heart’ (OH) revealed multilayered resistance mechanisms: WA exhibited 19.33% thicker leaves and significantly smoother epidermis (P < 0.05), alongside 3.11-fold higher leaf wax content dominated by C28-C32 fatty acids, primary alcohols, and alkanes. Scanning electron microscopy at 24 h postinoculation (HPI) demonstrated WA’s structural defenses via significantly lower hyphal colonization and smaller stomatal apertures. Transcriptomic profiling identified six cuticular wax biosynthesis genes upregulated in OH at 24 HPI, whereas WA prioritized constitutive defenses with only two induced wax transporter genes (TRINITY_DN9458_c1_g1 and TRINITY_DN1615_c0_g1). These findings provide insights into the role of leaf tissue epidermal waxes in the hydrangea resistance to leaf spot disease, laying a foundation for understanding disease resistance mechanisms and breeding for disease-resistant hydrangea cultivars.