Tissue and cellular localization of proteinase inhibitors I and II in the fruit of the wild tomato, Lycopersicon peruvianum (L.) mill

Abstract

The cellular and subcellular localization of proteinase inhibitor I and inhibitor II proteins in the fruit of the wild tomato species Lycopersicon peruvianum (L.) Mill., LA107 was determined by immunoanalysis of tissue blots and protein-A gold immunocytochemistry. Tissue blot analysis showed that the proteinase inhibitor I proteins were located throughout the fruit tissue, with the exception of the seeds. Light microscopy, using immunocytochemical labeling, indicated that all the parenchyma cells of the pericarp contained inhibitor I and II proteins in dense vacuolar protein aggregates that were not membrane bound. The size, number, and morphology of the aggregates within individual cells varied greatly. The funiculus, ovule, and early embryonic tissues were devoid of inhibitor I and II. Immunocytochemical analysis using transmission electron microscopy confirmed that the proteinase inhibitor I proteins were principally located and stored in protein aggregates within the vacuole of the fruit parenchyma cells. Some cytoplasmic protein-A gold immunolabeling of inhibitor I proteins was evident, which may be related to the synthesis and intermediate transport steps preceding storage of the inhibitor I proteins in the vacuoles.