Protein reserve hydrolysis in Douglas-fir seeds (Pseudotsuga menziesii [Mirb.] Franco) following feeding by the western conifer seed bug

Nymphs and adults of the western conifer seed bug, Leptoglossus occidentali s Heidemann (Hemiptera: Coreidae) feed on maturing seeds of many economical ly important coniferous tree species in natural stands and seed orchards th roughout western North America. Changes to the profiles of soluble (matrix) and insoluble (crystalloid) protein reserves of mature Douglas-fir seeds w ere examined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) to assess reserve hydrolysis caused by feeding of the seed bug. The major soluble and insoluble storage proteins of Douglas-fir seeds were rapidly hydrolyzed following feeding by L. occidentalis, in which female ad ults appeared to be more efficient in hydrolyzing seed reserves than adult males or nymphs. The higher molecular weight (34.5-39.5 kDa) acidic subunit polypeptides of the crystalloid protein complex (fractionated by SDS-PAGE under reducing conditions) were almost completely hydrolyzed in seeds susta ining as little as light feeding damage, in which > 66% of seed contents re mained (as determined by radiographic analysis). Only traces of crystalloid protein remained in seeds that had sustained severe damage, in which < 33% of the seed contents remained. Similarly, the major matrix (soluble) stora ge proteins also underwent rapid hydrolysis. Hydrolysis of soluble storage proteins following germination of Douglas-fir seeds showed striking similar ities to that induced by seed bug feeding and hydrolysis of insoluble cryst alloid proteins, albeit slower in germinated seeds, led to similar soluble breakdown products as those produced in fed-on seeds.