Phytotoxic sites of action for molecular design of modern herbicides (Part 2): Amino acid, lipid and cell wall biosynthesis, and other targets for future herbicides

A bird's eye review was tried in Part 2 of this series, 'Phytotoxic sites of action for molecular design of modern herbicides', in order to select the best selection of known and some novel plant-specific targets for molecular design of modern herbicides, which affect amino acid, lipid and cell wall biosynthesis. Although amino acid biosynthesis pathways, particularly those for aromatic amino acids, ammonia assimilation and branched amino acids, have been confirmed as reasonable herbicidal target domains, the other targets affecting plant growth more markedly than inhibition of 5-enolpyruvylshikimate-3-phosphate synthase, glutamine synthetase and acetolactate synthase are discussed. In three essential enzymes involved in fatty acid biosynthesis in or in the vicinity of chloroplasts, acetyl-CoA carboxylase (ACCase), elongase(s) for very long chain fatty acids (VLCFA) and linolate monogalactosyldiacylglycerol desaturase, ACCase and elongase are more important targets for new herbicides. Although the effect of cellulose biosynthesis inhibitors is restricted to cell wall formation in growing plant cells only, there is a good chance to design the low-use rate herbicides also in this class of inhibitors. Other possible targets for new herbicides are also discussed.