Molecular characterization of the heat shock transcription factors in switchgrass highlights PvHsf16 conferring cadmium stress

Heat shock transcription factors (Hsfs) play crucial roles in plants' responses to abiotic stress. However, the identification of <i>Hsf</i> family genes and their stress tolerance functions in switchgrass are less well studied. This study aimed to screen and identify <i>PvHsf</i> genes from the whole genome of switchgrass. A total of 51 <i>PvHsfs</i> were identified and categorized into three classes: Class A (<i>PvHsf01</i>−<i>PvHsf28</i>), Class B (<i>PvHsf29</i>−<i>PvHsf42</i>), and Class C (<i>PvHsf43</i>−<i>PvHsf51</i>). Collinearity analysis revealed that 46 <i>PvHsfs</i> had 42 collinearity relationships, and <i>PvHsf49</i> and <i>PvHsf50</i> were a pair of tandem duplicate genes. Developmental and stress-regulatory expression patterns of <i>PvHsfs</i> were also analyzed in various tissues and developmental stages or under NaCl, PEG, ABA, and CdCl₂ treatments. Nine <i>PvHsfs</i> were responsive to CdCl₂-treatment, including <i>PvHsf3</i>, <i>PvHsf4</i>, <i>PvHsf16</i>, <i>PvHsf19</i>, <i>PvHsf23</i>, <i>PvHsf24</i>, <i>PvHsf35</i>, <i>PvHsf44</i>, and <i>PvHsf45</i>, which were evaluated for their roles in cadmium (Cd) tolerance. By ectopic expressing these <i>PvHsf</i> genes in a Cd-sensitive yeast mutant, yeast cells expressing <i>PvHsf3</i> and <i>PvHsf16</i> exhibited higher Cd tolerance and the best result was by expressing <i>PvHsf16</i>. PvHsf16 was subcellularly localized in the nucleus. Expressing <i>PvHsf16</i> in Arabidopsis led to enhanced Cd tolerance with significantly higher Chl content, root length, and biomass compared to the WT plants under CdCl₂ treatment. Knowledge gained from this study will facilitate further functional analysis of <i>PvHsfs,</i> particularly <i>PvHsf16,</i> for molecular breeding of switchgrass and other related grass species.