Plants must adapt their development to environmental conditions, including rising temperatures due to climate change. Heat stress significantly impacts plant physiology, and to mitigate these effects, plants have evolved heat shock responses (HSR), with Heat Shock Factor A1a (HSFA1a) serving as a master regulator in Arabidopsis thaliana. Under nonstress conditions, HSFA1a remains cytosolic and inactive, bound to heat shock proteins (HSPs). Heat stress triggers HSP dissociation, enabling HSFA1a nuclear translocation, trimerization, chromatin binding, and activation of stress-responsive genes. Recent studies reveal that HSFA1a might act as a pioneer transcription factor to access closed chromatin regions and initiate HSR. Additionally, preliminary findings also suggest that HSFA1a undergoes liquid-liquid phase separation (LLPS) to form nuclear condensates that regulate gene expression. This project aims to 1) explore how temperature affects HSFA1a structure and oligomerization, 2) investigate LLPS of HSFA1a with and without DNA, 3) characterize HSFA1a pioneer activity, and 4) determine the physiological importance of LLPS in HSR.