*3.2. High Level of CsHCT Expression in the Stem Tissues of Tea Plants and Seedlings*

To assess *CsHCT* expression in tissues of tea plants and seedlings, we selected YL, OL, YS, and OS tissues from 1-year-old tea seedlings and extracted the total RNA. Reverse transcriptase was then used to synthesize the first cDNA for qRT-PCR analysis. The results indicated that the *CsHCT* expression level was the highest in YS tissues, followed by OS tissues, buds, and leaves in tea seedlings (Figure 3A). The transcription level was the highest in OS tissues, followed by YS, YL, and OL tissues in tea plants (Figure 3B). Nonlignified YS tissues in tea seedlings exhibited the highest CsHCT expression level, but in tea plants, the CsHCT expression level was high in both OS and YS tissues. Moreover, CsHCT expression was evident in the buds and YL tissues of both tea plants and seedlings; however, expression levels remained lower than those in stem tissues (Figure 3).

**Figure 3.** CsHCT transcription levels in various tissues of tea plants; qRT-PCR analysis of CsHCT transcription levels in various tissues of (**A**) tea seedlings and (**B**) tea plants. Total RNA was isolated from young leaf (YL), old leaf (OL), young stem (YS), old stem (OS), and buds. CsHCT transcription levels were determined. Relative amounts of transcripts were calculated and normalized to that of *18S rRNA*. Values represent means ± SD from three biologically independent experiments. Values with different letters are significantly different at *p* < 0.05, according to a post hoc least significant difference (LSD) test.
