Genetic engineering techniques are essential for both plant science and agricultural biotechnology, enabling functional genomics studies, dissection of complex traits, and targeted crop improvement. Among the various genetic tools currently in use, clustered regularly interspaced short palindromic repeats-CRISPR-associated protein (CRISPR-Cas)-based genome editing has emerged as a transformative technology due to its precision, versatility, and ease of use. In particular, CRISPR-Cas9 has become the most widely adopted platform for genome manipulation in plant systems, including maize, owing to its high editing efficiency, multiplexing capabilities, and scalability for diverse applications. This review highlights the biological significance and technical considerations necessary to implement CRISPR-Cas9 in maize. We discuss critical components for successful editing, including the selection of strong and tissue-appropriate promoters for Cas gene and guide RNA expression, codon optimization of Cas nuclease genes, effective guide RNA design, and multiplexing strategies using RNA polymerase III (Pol III)- or Pol II-dependent promoter-driven polycistronic expression systems. Additionally, we provide insights into vector construction methodologies and reliable genotyping techniques to detect and validate genome edits. Together, these elements constitute a practical framework for deploying genome editing in maize research and breeding. By optimizing these parameters, researchers can enhance the efficiency and accuracy of CRISPR-mediated genome modifications, accelerating functional genomic discovery and the development of improved maize varieties tailored to meet future agricultural demands.
