Genome-Wide Identification, Expression Analysis of HSF Gene Family in Lanzhou Lily (Lilium davidii var. unicolor) and Screening of Key Genes LdHSF10 and LdHSF40 in Response to High-Temperature Stress

The heat shock transcription factor (HSF) family is a core regulatory component for plants in response to adversity stress and plays a pivotal role in regulating plant reactions to abiotic stress. Lanzhou lily (Lilium davidii var. unicolor) is an economically and horticulturally important bulbous crop widely cultivated in Northwest China, and its growth and yield are severely threatened by high-temperature stress during the growing season. Although HSF genes have been extensively and thoroughly investigated in other plant species, their functional characterization in lilies remains elusive. In this study, a total of 41 LdHSF genes were identified from the genome of Lilium davidii var. unicolor using bioinformatics approaches. The proteins encoded by these genes exhibited considerable variations in the number of amino acids (aa), as well as distinct isoelectric points (pI) and instability indices. Phylogenetic analysis classified these 41 LdHSF genes into three subfamilies (A, B and C). Promoter analysis revealed that the promoters of most LdHSF genes were rich in light-responsive cis-elements. Meanwhile, the promoters of some genes were highly abundant in hormone-responsive cis-elements, whereas those of other genes were enriched in stress-responsive cis-elements. Gene expression heatmaps and transcriptomic data demonstrated that the expression patterns of LdHSF genes showed significant differences in various tissues and under heat treatment. Based on transcriptomic and RT-qPCR data, we further screened out LdHSF10 and LdHSF40 as the major genes responding to heat stress. Functional experiments verified that these two genes encoded nuclear-localized proteins with transcriptional activity. Collectively, these findings lay a solid foundation for elucidating the molecular mechanisms underlying the regulation of heat tolerance by HSF transcription factors (TFs) in lilies in future research.