Abstract
Molecular chaperones HSP70 and HSP90 represent a critical, yet conflict-ridden, node in plant physiology, particularly under the dual impact of heat stress and viral infection. As key components of both thermotolerance (maintaining proteostasis) and innate immunity (stabilization of NLR receptors), they are simultaneously exploited by viruses to facilitate their own life cycle. This review critically analyzes this "trilemma," focusing on the hypothesis of competition for a limited chaperone pool. We present mechanistic insights indicating that during heat stress, cellular priority shifts towards maintaining global proteostasis, thereby diverting chaperones from immune functions. This resource-based competition mechanism potentially explains the collapse of ETI-immunity, as NLR receptors, deprived of support from the HSP90-SGT1-RAR1 complex, are destabilized and targeted for degradation. We also integrate adjacent signaling pathways into this model, including hormonal cross-talk (SA, JA) and autophagy. Understanding this trade-off opens new perspectives for molecular breeding and the biotechnological engineering of stress-resilient crop varieties.