Advancements in balancing glucosinolate production in plants to deliver effective defense and promote human health

Glucosinolates (GSLs) are a prototypical group of bioactive compounds found in the Brassicaceae family that promote human health and plant defense. The GSL-myrosinase system can be induced to release multiple bioactive products when plants are subjected to mechanical damage, environmental stress, or pathogen infection. While many GSLs promote human health, some cause deleterious effects when ingested. To engineer Brassicaceae crops with lower levels of harmful GSLs without sacrificing health-promoting GSLs requires a complete understanding of the origin and advances in GSL modification. Extensive early domestication studies were conducted using classic breeding and plant nutrition. More recently, genetic modification of specific groups of GSLs or levels of GSLs in specific tissues has been partially successful. However, efforts have fallen short of delivering a reduction in potentially harmful GSLs without concomitant losses to health-promoting effects and plant defense. The latest work has been to synthetically express GSL biosynthesis pathways in non-host crops or microbial species. However, yields have been far from economically sustainable. This review discusses key advances made in GSL modification that are promising for the precise modification of GSL content and composition for optimal plant defense and human health.