GENOME EDITING FOR ENHANCING ABIOTIC STRESS TOLERANCE IN MAIZE: MOLECULAR MECHANISMS, PHYSIOLOGICAL RESPONSES AND FUTURE PROSPECTS

Abstract

Maize (Zea mays L.) is one of the major crops that contribute to food security worldwide and is increasingly exposed to abiotic stresses like drought, heat, and salinity stress, worsened by climate change. The polygenetic nature of stress tolerance and long breeding cycles are the limitations of conventional breeding approaches. This review provides a summary of recent advances, molecular and physiological mechanisms and perspectives of precision genome editing such as CRISPR-Cas9 systems and TALENs to improve abiotic stress resistance in maize. We identify important molecular networks that underpin responses to stress including, among others, DREB/NAC transcription factor networks for drought, HSFs/HSPs networks for heat and HKT/NHX networks for salinity. Promoter changes were successfully made in ARGOS8, conferring a 5 bushels per acre (around 8 10% yield improvement) advantage under drought conditions, and the knock-in of the teosinte-derived ZmHKT1;2 allele, which lowered shoot Na⁺ by 80% in saline conditions. While there are concerns about the possible off-target effects, delivery efficiency and regulations, genome editing has the potential to revolutionize maize breeding for climate resilience. The translational capacity of editing technologies is highlighted in this review for the purpose of protecting global food systems from a changing climate.