3.7 The distribution and subcellular localization of CsTPS1 and CsTPS1-AS differ
Monoterpenes are synthesized exclusively by plastids in higher plants; thus, plant monoterpene synthases are localized to the chloroplast. To verify this prediction, the two CsTPS1 and CsTPS1-AS proteins were fused to the N-terminal of eYFP, and the fusion proteins were transiently expressed in tobacco leaves. The eYFP signals of CsTPS1 and CsTPS1-AS fusion proteins were consistent with chlorophyll autofluorescence and showed no overlap with the cytosolic mCherry signals from the negative controls (Figure 6C). These findings confirmed that the two CsTPS1 and CsTPS1-AS proteins are localized to the chloroplast. However, the distribution and localization of the CsTPS1 and CsTPS1-AS proteins in the chloroplast varied (Figure 6C). The CsTPS1 protein is likely localized in the stroma of the chloroplast and exhibits a highly homogeneous distribution. Conversely, the CsTPS-AS protein might be localized to the outer membrane of the chloroplast and exhibit a sporadic distribution (Figure 6C). The distribution and localization ofCsTPS1 and its AS forms in the chloroplast differ, and this might explain the distinct levels of disease resistance that they confer to tea plants.