HSPA4 and viral infectious disease: To determine how PVY infection affects the moderate heat stress response of Gala and Chicago, we analyzed HSP genes belonging to three subfamilies: HSP20, HSP70 and HSP90. It was previously shown that HSP20 (HSP20-21 used in this work) is significantly up-regulated in potato under heat stress (Zhao et al., 2018), whereas HSP70, in addition to its function in response to heat stress, plays several roles in virus infections (reviewed in Nagy and Pogany, 2010).