4.2 CsTPS1 is involved in regulating the defense response
via AS in tea plants
The transcriptional regulation of TPS genes is critically
important for volatile terpenoid biosynthesis (Nagegowda, 2010. The
substrate and product specificity of TPS s can regulate terpenoid
biosynthesis at the enzyme level (Fischer et al., 2013). In addition to
regulating transcriptional processes such as splicing, TPS genes
also regulate other complex aspects of transcription. AS, which produces
multiple mRNA subtypes from a single gene, is widespread in plants and
often produces a variety of transcripts with diverse functions (Reddy et
al., 2013). The full-length sequences and short AS forms ofCsTPS1 were obtained from the young leaves of tea plants.
Although both CsTPS1 and its AS forms could catalyze the
formation of geraniol in vitro , CsTPS1 and its AS forms
confer different levels of disease resistance. The expression ofCsTPS1-AS , but not the full-length sequences of CsTPS1 ,
was induced in response to pathogen infection (Figure 5C and 5G). This
might explain differences in the distribution and localization of CsTPS1
and CsTPS1-AS in the chloroplasts.
The silencing of CsTPS1-AS significantly decreased the content of
geraniol and the resistance of tea plants to infection by the two
pathogens (Figure 5B and 5C); however, no changes in disease symptoms
were observed when CsTPS1 was silenced (Figure 5G and 5H). Hence,
the shorter AS form of CsTPS1 plays a critical role in enhancing
the resistance of tea plants to pathogen infection.