From pollen precursor to totipotent embryo: a model system for plant cell developmental plasticity.

Androgenesis, the stress-induced reprogramming of microspores into doubled haploid plants, remains a pivotal yet persistent constraint in contemporary plant breeding programs. During this dramatic fate re-specification, committed gametophytic cells regain totipotency, which is controlled by a complex signaling network that converts external stress signals into an organized developmental program. Stress-induced reactive oxygen species (ROS) function as secondary messengers, whose signaling capacity is unlocked by a robust antioxidant system that maintains redox homeostasis. Subsequently, triggered programmed cell death (PCD), through apoptotic and autophagic pathways, executes a selective dismantling of compromised microspores and mediates extensive cytoplasmic clearance. This internal reprogramming is complemented by extracellular modifications, including dynamic cell wall remodeling that enhances cellular plasticity, and the establishment of embryonic polarity via auxin gradient establishment. Together, these pathways-ROS signaling, controlled PCD, cell wall dynamism, and auxin-driven patterning-constitute a regulatory circuit that authorizes the switch from gametophytic to sporophytic identity. Elucidating the integrated signaling network that reprograms microspores into embryos enables the rational design of interventions to unlock embryogenic potential across recalcitrant genotypes. This foundational knowledge is essential for engineering robust, genotype-independent protocols to accelerate trait fixation, genome editing, and cultivar development.