Phenylalanine and Abiotic Regulation of Early Defense

Ultraviolet (UV) radiation and visible light are required for appropriate photomorphogenic and other developmental processes in seedlings. Stress responses early postgermination have received little attention in many intensively bred plants of economic interest, particularly how carbon and nitrogen may be utilized under different yet expected pressures. We have examined germination, seedling growth, and subcellular responses to ROS-inducing abiotic stress in germinating and young seedlings in response to UV and cold abiotic signals. We have investigated how phenylalanine, a key substrate in the phenylpropanoid pathway, may be involved in these responses in young seedlings of broccoli and soybean. We observed that signs of stress (failure to germinate or delayed germination, cessation of elongation, ROS et al.) were reduced if phenylalanine were provided before germination, during imbibition in seeds germinated in darkness. Moreover, seedling vigor in white light growth was improved with provision of phenylalanine, but only at specific points in development. Phenylalanine provision impacted both subcellular pools of phenylpropanoids, and also cuticular attributes of photosynthesizing leaves. Overall, these data indicate that breeding efforts can target management of nutrient delivery in the seed-to-seedling transition to reduce seedling loss due to stress, and minimizing later loss of yield.