3.6 CsTPS1 and its AS forms confer different levels of disease resistance
To compare the function of CsTPS1 and its AS forms in regulating geraniol formation and pathogen resistance in tea plants,gene-specific AsODNs were designed to silence CsTPS1 and its AS forms (Table S1). The geraniol content was lower in tea leaves in which the expression of CsTPS1-AS was suppressed compared with that in control plants at 12, 24, and 48 h, respectively (Figure 5A and 5B). As expected, CsTPS1 -AS -silenced tea plants were more susceptible to infection with both C. gloeosporioides andNeopestalotiopsis sp. (Figure 5C) at 72 hpi, as the average surface area of disease spots on the tea leaves was larger inCsTPS1-AS- silenced tea plants compared with that in control plants (Figure 5D). By contrast, when CsTPS1 was successfully suppressed in tea leaves (Figure 5E), the geraniol content was not change in tea leaves (Figure 5F) in which the expression ofCsTPS1 was suppressed compared with that in control plants at 12, 24, and 48 h, respectively. Meanwhile, no difference in the susceptibility of tea leaves to pathogen infection was observed betweenCsTPS1 -silenced tea leaves and control tea leaves at 72 hpi (Figure 5G and 5H).
WGA staining was used to observe the hyphal growth ofNeopestalotiopsis sp. and C. gloeosporioides on tea leaves. After WGA staining, the hyphae emitted a green fluorescence under the microscope. The green fluorescence intensity ofCsTPS1-AS -silenced tea leaves was higher than that of control tea leaves (Figure 6A). The extent of mycelial growth onCsTPS1-AS -silenced tea leaves was higher than that on control leaves (Figure 6B).
These findings indicate that CsTPS1 and its AS forms perform distinct functions in both geraniol formation and pathogen resistance in tea plants and that CsTPS1 plays a role in regulating geraniol biosynthesis and pathogen resistance via AS.