Plant synergid embryonic potential is unlocked following egg cell collapse.

Cell-cell communication is indispensable for cell specification and differentiation throughout plant reproduction. The egg cell and its sister synergid cell have long been considered closely coordinated partners during fertilization, yet the nature of this interplay and their specific roles remain unclear. Here, we show that synergid cells could acquire the competence to initiate cell division for embryogenesis following egg cell collapse. Unlike the traditional view, synergid cells appear to take over the egg cell role without undergoing fate conversion to adopt the egg cell identity. These findings suggest that synergid cells possess an intrinsic embryogenic potential, which is specifically unlocked upon egg cell collapse, thus enabling embryogenic initiation in the absence of a functional egg cell. Building on this discovery, we established an in planta haploid-induction system independent of conventional haploid-inducing genes. Importantly, this system also functions in tomato, a distantly related dicotyledonous crop, thus offering a broad conceptual framework for engineering haploid production across diverse plant species.