It's gall relative: metabolic profiling of two morphologically distinct oak leaf galls induced by cynipid wasps

Plant galls are outgrowths on plant tissue induced by another organism.Galls benefit the inducer, which can come from a wide range of kingdoms, including bacteria, fungi, nematodes, plants, mites and insects (Gatjens-Boniche 2019, Harris and Pitzschke 2020).Gall formation differs from regular plant development.They display a variety of forms depending on their inducer and the species and tissue of the host, and are referred to as an extended phenotype of the inducer.Galls can be part of a mutualistic relationship with the host, such as in plant root nodules, but they are often parasitic (Harris and Pitzschke 2020).These biotic interactions present a unique feat of bioengineering by the inducer, requiring genetic and structural reprogramming of the host.Galls induced by microbes are well studied compared to those of insects.They tend to be relatively structurally simple, and are also called tumors (Gatjens-Boniche 2019).A famous example is the crown gall induced by Agrobacterium tumefaciens (Nester 2015), which demonstrates how bioengineering in the natural world can be co-opted for bioengineering in the lab; Agrobacterium is now used extensively for plant genetic transformation.In contrast, galls induced by insects can be structurally complicated and diverse, especially those induced by cynipid wasps (Hymenoptera order, Cynipidae family) on oaks, also called oak gall wasps (Stone and Cook 1998).These wasps lay their eggs on oak tissues, and this action induces the formation of a gall structure around the eggs,