Functional Characterization Of Maize Seed Mutant Proline1

Proline, is an important amino acid, that accumulates in many plant species.Besides its role in plant cell responses to environmental stresses, the potentialbiological functions of proline in growth and development as a metabolite or a signalmolecule are unclear.Here we reported cloning and functional characterization of the maize (Zea mays)classic mutant proline responding1(pro1). pro1, also known as opaque6(o6),exhibits a collapsed and starchy endosperm and a lethal seedling phenotype. Itencodes a△1-Pyrroline-5-carboxylate synthetase (P5CS) that catalyses thebiosynthesis of proline from glutamic acid. Lost function of Pro1significantly inhibitsproline biosynthesis and decreases its accumulation in pro1mutant. Prolinedeficiency results in an increased level of uncharged tRNApro AGGaccumulation andtriggers the phosphorylation of eukaryotic initiation factors2(eIF2) in pro1mutant.This causes a general reduction of protein synthesis in mutant.Proline deficiency also down-regulates major cyclin genes at the transcriptionallevel, causing cell cycle arrest and suppression of cell proliferation. These processesare reversible when external proline is provided, suggesting proline possible act as asignal molecule affecting cell cycle regulation.Together, the results demonstrate that proline plays an important role in theregulation of general protein synthesis and cell cycle transition in higher plants.