Evidence for an Atrial Natriuretic Peptide–-Like Gene in Plants

The presence of a gene found in the animal kingdom expressing a peptide hormonal system in plants has never been demonstrated. However, there is at least one potential hormonal system in plants (i.e., the atrial natriuretic peptide–-like hormonal system) based upon high-performance gel permeation chromatography and radioimmunoassay evidence. In plants, atrial natriuretic–like peptides enhance the flow of water up stems to leaves and flowers. The present investigation was designed to determine within plants the presence of the atrial natriuretic peptide (ANP) gene as defined by Southern blot hydridization, indicating the presence of the ANP gene sequence, and by Northern blots assessing the ability of this gene to express ANP prohormone mRNA. Southern blots of English ivy (Hedra helix) genomic DNA revealed that the ANP gene sequence was present in its roots, stems, and leaves. Northern blot analysis of total plant RNA isolated from leaves, roots, and stems of Hedra helix revealed a single 0.85-kilobase prohormone ANP transcript in stems similar to that detected in rat heart. Semiquantitative analysis suggested that ANP gene expression was less in English ivy compared with that of rat heart atria but similar to the amount found in extra atrial rat tissues when corrected for total RNA when quantitated by 2D scanning. The demonstration of the ANP gene sequences and expression of the ANP-like gene in plants suggests that plants and animals may have evolved much more similarly than previously thought.