A paper in the newest Proceedings of the National Academy of Sciences examines intimately how one weed, Amaranthus tuberculatus (waterhemp) developed resistance to a class of herbicides referred to as protoporphyrinogen oxidase inhibitors. PPO is the last, very important enzyme step within the pathway that leads to chlorophyll, the inexperienced pigment that allows plants to convert sunlight into extra consumer-friendly vitality. Waterhempâ€™s resistance is outstanding on two counts First, it includes the loss of not one but two targets for the weedkiller. Secondly, the mutation that delivers resistance is the lack of a complete amino acid within the goal. Resistance mutations generally contain a change to a single letter of the DNA code. Waterhemp has lost three complete letters, a complete amino acid. A commentary by Jonathan Gressel and Avraham Levy explains the science at a barely more accessible level than the waterhemp paper itself, however it does far more. It makes plain simply how efficient agriculture is as â€œthe selector of improbable mutationsâ€.