Dissection of additive, dominant, epistatic roles of allelic variation within heat shock factor genes in Chinese indigenous poplar ( Populus simonii )

Heat shock transcription factors (Hsfs) play a crucial role in plant growth and development, but the significance of Hsfs is not clearly understood in long-lived perennial plants. Here, two class A Hsf members (PsHsfA1c1 and PsHsfA7a1) were identified in Populus simonii, an important and pioneering species in northern China, using bioinformatics analysis and molecular cloning. Tissue-specific expression profiling showed that both Hsfs contained high transcript abundance in mature leaf, mature xylem, and root; also, their expression patterns varied in response to multiple abiotic stresses, such as temperature, drought, salt, hormone, and sugar, suggesting that Hsfs are essential in plant responses to diverse abiotic stresses. Based on nucleotide diversity (π T = 0.00772, θ w = 0.01519 and π T = 0.00392, θ w = 0.00899) and linkage disequilibrium tests (LD, r 2 ≥ 0.1, within 1200 and 700 bp, respectively) within PsHsfA1c1 and PsHsfA7a1 in a P. simonii association population (607 unrelated individuals), we identified 45, 49, and 26 associations consistent with additive, dominant, and epistatic effects, conferred by multiple variants within both genes across 12 morphological and physiological traits. In which, three significant SNPs (PsHsfA1c1_2273, PsHsfA7a1_308, and PsHsfA7a1_2595) exhibited significant differences of transcript abundance among their genotypic classes in the association population. The results observed here will be useful to understand their potential roles in tree growth, development, and response to environmental stresses.