CRISPR-Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease) is a formidable and precise gene-editing system, invented as a natural immune system of bacterial defense. The system relies on a guide RNA/CrRNA (Crispr RNA) sequence, specifically designed to bind to the target nucleic acid, enabling the Cas nuclease to act like a molecular scissor and cleave the target sequence. Recent research has substantially advanced the development, optimization, and application of Cas nucleases, particularly Cas9, Cas12, and their engineered orthologs to enhance the fidelity, flexibility, and proficiency of specific edits at the target site. This review focuses on the latest advancements in the research on Cas nucleases such as Cas9, Cas12a, Cas12b, CasΦ, Cas13, and Cas14, along with their mode of function and the exclusive features of each nuclease. Further, we have elaborated on the emergence of redesigned Cas9 orthologs, such as dCas9 (deactivated Cas9) and nCas9 (Cas9 nickase). The modified Cas9 orthologs have empowered the CRISPR-based editing with sophisticated techniques such as base editing and prime editing, which are capable of providing preferred edits with more precision and specificity. These advanced genome editing approaches have been favorably employed to improve the desirable agronomic traits such as stress tolerance, herbicide resistance, and yield stability in a wide range of crops, including rice, maize, wheat, tomato, and cotton. KEY MESSAGE: Our manuscript offers the recent advancement in the research on Cas nucleases, and their modified orthologs to perform CRISPR-based gene edits with enhanced more precision and specificity.
