Arabidopsis heat stress transcription factors A2 (HSFA2) and A3 (HSFA3) function in the same heat regulation pathway

Abstract

Heat stress transcription factors (HSFs) play an essential role in the adjustment of plants to high temperatures. These molecules have evolved complicated mechanisms that rely on interactions between different HSFs and other heat stress-related genes [such as bZIP28, multiprotein bridging factor 1c (MBF1c), calmodulin-binding protein kinase 3 (CBK3)] in response to different heat stresses (such as occasional or successive high temperatures). In the present study, phenotypic, gene expression and yeast two-hybrid assays revealed that HSFA2 and HSFA3 function in the same heat regulation pathway. The single mutants, hsfa2 and hsfa3 as well as double mutant hsfa2 and hsfa3, exhibited heat-sensitive phenotypes in acquired thermotolerance after a long recovery time (ATLR) but not in basic thermotolerance and acquired thermotolerance after a short recovery time (ATSR). The expression of HSP18.1-CI and HSP25.3-P was down-regulated in single and double mutants of hsfa2 and hsfa3 under successive heat stress in ATLR assays. In addition, HSFA2 interacted with HSFA3 at the protein level in yeast two-hybrid assays. These results demonstrated dynamic alterations in the expression of HSFA2, HSFA3 and other heat-related genes in ATLR assays, providing new insights into the relationship between HSFA2 and HSFA3; this information will refine the HSF network in the regulation of heat stress response.