Identification and Expression of CsUGT Alleles Based on Haplotype-resolved Genomes of Camellia sinensis Jinguanyin

Objective Key genes responsible of generating uridine diphosphate glycosyltransferase (UGT) that catalyzes the glycosylation of the secondary metabolism associated with the stress response of Camellia sinensis were identified, and expressions under stress analyzed to decipher the aroma formation of oolong tea in processing.

Method Based on the haplotype-resolved genomes of C. sinensis Jinguanyin, CsUGT alleles were analyzed by bioinformatics and RT-PCR. Expressions of CsUGT at 0, 3, 6, 12, and 24 h under stresses of low temperature (4℃), drought (10% PEG-6000 solution), or hormone (100 μmol·L⁻¹ MeJA solution) as well as in the young leaves, withering, post-1^st turning-over, post-2^nd turning-over, post-3^rd turning-over, and before firing in the processing stages of Jinguanyin oolong tea were determined.

Result The 142 CsUGT allele pairs identified from the haplotype-resolved genomes were mostly in the chloroplasts and could be divided into 5 subfamilies based on the evolutionary tree. These alleles were conserved and similar in structure when came from the same parent. Expressions of most of the alleles were tissue specific playing an important role in different organs of the tea plant. The expressions of CsUGT002, CsUGT047, and CsUGT091 peaked at 6h under MeJA treatment, while some peaked in 3 h under cold stress and 24 h under drought conditions. The expression of CsUGT115 was significantly upregulated during processing, while some others peaked at the 3^rd turning-over stage.

Conclusion Most CsUGTs were acidic, hydrophilic, and found in the chloroplast. Expressions of CsUGT alleles were tissue specific. Some CsUGTs associated with the aroma synthesis were activated by the stresses exerted by the tea processing.