Developmental Variation in Tea Polysaccharide Characteristics Is Associated with Phytohormonal and Transcriptional Changes

Tea polysaccharide preparations obtained from five successive leaf positions (L1–L5) and stem tissue (S) of Camellia sinensis cv. Rougui were compared to characterize developmental variation in their physicochemical and functional properties. Extraction yield increased from L1 to L4 and then declined, while neutral sugar content generally increased with leaf maturity. Monosaccharide composition and apparent molecular weight distribution also varied markedly, with peak molecular weight increasing from 70.5 kDa in L1 to approximately 804 kDa in L4 and L5. Antioxidant activities differed among assays and were associated more consistently with protein and tea polyphenol contents than with individual carbohydrate traits, indicating that the measured activities reflected the composite composition of the crude polysaccharide preparations. Phytohormone profiling and transcriptomic analysis of four representative tissues (L2, L3, L4, and S) showed tissue-dependent variation in endogenous hormone profiles and in genes related to carbohydrate metabolism, nucleotide-sugar interconversion, galacturonan-related biosynthesis, and pectin-related modification. Exploratory tissue-level correlations were used to prioritize 14 candidate genes associated with representative polysaccharide traits. Given the limited number of shared tissue types included in the integrated analyses, these associations remain exploratory and do not provide evidence for direct hormonal or transcriptional regulation. Overall, tea polysaccharide characteristics varied substantially with leaf developmental position and tissue type, supporting the selection of tea raw materials according to targeted polysaccharide properties.