Recent Advances in Seedling Research: Phenylalanine and Phenylalanine Ammonia-Lyase (PAL)

Phenylalanine is an aromatic amino acid that plants synthesize, then metabolize, to make other chemical structures, defense mechanisms, and yet undiscovered functions via multiple genes. In the early vegetative stages of life, phenylalanine plays important roles in germination, organelle development, tissue and cell development, and function. The family of Phenylalanine Ammonia-Lyase (PAL) enzymes also play roles in the seed-to-seedling transition, although, while being the first enzyme (but not the sole enzyme) in the phenylpropanoids pathway, not all roles have been elucidated. In this review of recent literature on phenylalanine and PAL’s impact on seedlings and seedling establishment, it is clear from the last 5–10 years, in particular, that major advances have been made in chemistry, molecular, protein studies, and in silico studies. It is exciting that many chemical and molecular advances have been applied to plants of economic importance including agriculture, horticulture, and in medicinal chemical production utilizing the actions of phenylalanine and PAL.