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.