Metabolic engineering of vegetative organs for enhanced oil accumulation in biofuel feedstocks

Plant oils are increasingly sought after as sustainable sources of bioenergy for biodiesel production and high-value biochemicals. Although oilseed crops currently serve as the primary source of plant oils, meeting the rising global demand on limited arable land, without compromising food security, remains a major challenge. Therefore, metabolic engineering of high-biomass bioenergy feedstocks has been widely explored to enhance the conversion of carbon stored in vegetative tissues into energy-dense triacylglycerol (TAG). Significant progress has been made in boosting TAG accumulation in the vegetative tissues of various plant species through bioengineering strategies. These efforts span from single-gene modifications to the coordinated expression of key lipogenic factors such as WRI1, DGAT1/2, and OLE1. The resulting fatty acid and TAG profiles, however, often vary depending on the targeted plant species and promoter(s) used. This review summarizes the roles of essential lipogenic factors in plant oil biosynthesis and highlights recent advances in metabolic engineering across diverse crop species through combinatorial expression of these factors. We also discuss future strategies for achieving high-level oil production without incurring growth penalties. By offering new perspectives on metabolic engineering, this work aims to support the development of plants as efficient biofuel feedstocks, contributing to the global effort to address energy challenges.