Compact Cas12 Systems for Multiplex Engineering of Plant Abiotic-Stress Networks

Compact CRISPR-Cas12 platforms, particularly miniature and hypercompact effectors such as Cas12f, Cas12j/CasPhi, and Cas12lambda, are emerging as delivery-efficient tools for plant genome engineering because their reduced coding size facilitates viral-replicon and other size-constrained delivery routes while supporting dense guide multiplexing. Here, we argue that their highest value for crop improvement lies not simply in additional nuclease choices, but in programmable, systems-level tuning of abiotic-stress defense layers, including ion homeostasis, redox buffering, osmotic adjustment, abscisic acid (ABA)-centered hormone signaling, and transcriptional control. We distinguish evidence already demonstrated in stable plants, transient plant assays, or protoplasts from approaches extrapolated from Cas9/Cas12a or non-plant systems, and emphasize that many compact Cas12 applications remain platform-building rather than field-ready technologies. Current plant evidence supports Cas12a as a mature multiplex-editing and transcriptional-repression platform, Cas12f as a rapidly improving mini-editor with stable and viral-delivery demonstrations, and Cas12j/CasPhi as a hypercompact system with recent crop-editing and base-editing potential. By contrast, Cas12g, Cas12h, Cas12lambda, and TnpB-like nucleases are best viewed as promising future modules until plant-active implementations are broadly validated. We offer a forward-looking roadmap in which compact Cas12 systems complement Cas9 and Cas12a by enabling rapid target triage, promoter and untranslated-region engineering, transient CRISPR activation/interference, and stepwise assembly of durable sentinel edits. Translation will depend on improving efficiency and fidelity across genotypes, reducing mosaicism, documenting off-target and structural variation in multiplex stacks, and aligning delivery strategies with regulatory expectations for transgene-free crops.