Regulatory Responses of Ectothermic Embryos to Predicted Heat Stresses Under Near-Future Climate Change.

Heat stress can disrupt coordinated regulatory processes underpinning normal development, resulting in embryonic malformation and inviability. Embryonic buffering against thermal challenge may therefore play a crucial role in individual survival and population resilience under heat stress. Yet, the molecular mechanisms underpinning embryonic defence against ecologically-meaningful heat stresses remain poorly understood. We investigated the regulatory responses of brown anole (Anolis sagrei) embryos to three patterns of heat stress we find will increase under near-future climate warming. Across chronic, persistent, and acute heat treatments, embryos exhibited rapid transcriptome-wide disruption followed by recovery toward normal developmental trajectories within 24 h. Despite this broad perturbation, a core regulatory module governing forebrain and craniofacial development remained strongly preserved across heat insults. Heat stress induced widespread transcriptional suppression alongside increased reliance of post-transcriptional regulation and a dose-dependent slowing of RNA flux, consistent with mitigation of proteotoxic stress. Concurrently, embryos rewired regulatory networks through recruitment of extramodular stress-response genes and strengthening co-expression within developmental pathways. Together, these results reveal a hierarchical regulatory strategy in which embryos buffer essential developmental programs while flexibly reconfiguring peripheral networks to manage cellular stress. This systems-level resilience underscores the importance of early-life adaptive regulatory plasticity in shaping organismal responses to climate warming.