Intracellular localization of capsaicin and its analogues in Capsicum fruit II. The vacuole as the intracellular accumulation site of capsaicinoid in the protoplast of Capsicum fruit 1

The intracellular localization site of capsaicinoid, the pungent principle of hot pepper, was studied by Percoll density gradient centrifugation technique and by light and electron microscopy. Protoplasts prepared from the placenta of the hot pepper fruit, “Karayatsubusa” (Capsicum annuum var. annuum cv. Karayatsubusa), were used for subcellular fractionation by Percoll density gradient centrifugation. Capsaicinoid was detected at the top of the tube. The fraction containing the most capsaicinoid was collected for light and transmission electron microscopy. Capsaicinoid in the intact vacuoles was located in the same place as that in the protoplasts subfractionated by Percoll density gradient centrifugation. Transmission electron microscopy showed that the capsaicinoid-localized fraction had vesicle and vacuole-like structures, including electron-dense granules, similar to those observed in intact epidermal cells of the placenta. On the other hand, no electron-dense granule with a structure similar to that of the epidermal cells was found in the other fractions examined. Capsaicinoid probably is located mostly in the vacuole.