General Motors’ venture capital arm has invested in a California startup that’s making imitation leather from mushrooms. The material is made by MycoWorks using the root-like structures of mushrooms, called mycelia. It could provide an alternative to both traditional leather made from animal skins, usually cattle, and artificial leather made from plastics. The auto industry is the largest user of leather other than for shoes, according to 2015 data from International Council of Tanners. MycoWorks grows these threadlike mycelia into flexible, leather-like sheets. The resulting material feels like leather, has similar durability and can be colored using processes that do...