ATRIAL NATRIURETIC PEPTIDES ARE PRESENT THROUGHOUT THE PLANT KINGDOM AND ENHANCE SOLUTE FLOW IN PLANTS

The present investigation was designed to 1) determine if atrial natriuretic-like peptides are present throughout the plant kingdom and 2) to determine if these peptides increase the flow of solute and/or water upward to leaves and flowers of plants. The 126-amino acid prohormone of atrial natriuretic factor (proANF)-(l 30). proANF-(31-67), and atrial natriuretic factor (ANF)-like peptides were present in the roots, stems, leaves, and flower petals of the more highly developed plants (Tracheophyta), with their highest concentrations being: Florida beauty > buddhist pine > Boston fern > rose = geranium = resurrection plant or club moss > Moses-in-the-cradle > Florida coontie. These peptides were also present in Bryophata (plants without vascular tissue or roots) and even in Eugleno, flagellated chlorophyll-containing plants without leaves, stems, or roots. proANF-(1-30), proANF-(31-67), and proANF-(79-98) but not ANF (each at <5.9 pg/ml) significantly increased (P < 0.001) the flow of colored water up stems, coloring their flowers 15-35 min earlier than the other one-half of the same flowers without exogenous peptide addition. These same peptides increased the rate of transpiration (i.e., loss of water from the leaves) and the absorption of solutions. High-performance gel permeation chromatography revealed that proANF-(1-30), proANF-(31-67), and ANF extracted from plants are very similar to their pure synthetic human sequences, with elution profiles and molecular weights of the plant extracts duplicating those of the pure synthetic peptides.