(Below N is a link to NCBI taxonomic web page and E link to ESTHER at designed phylum.) > cellular organisms: NE > Eukaryota: NE > Viridiplantae: NE > Streptophyta: NE > Streptophytina: NE > Embryophyta: NE > Tracheophyta: NE > Euphyllophyta: NE > Spermatophyta: NE > Magnoliophyta: NE > Mesangiospermae: NE > eudicotyledons: NE > Gunneridae: NE > Pentapetalae: NE > asterids: NE > Ericales: NE > Theaceae: NE > Camellia: NE > Camellia sinensis: NE
LegendThis sequence has been compared to family alignement (MSA) red => minority aminoacid blue => majority aminoacid color intensity => conservation rate title => sequence position(MSA position)aminoacid rate Catalytic site Catalytic site in the MSA MDSIAHDFPPFFRVHKDGRVERFMVSDYVPPAVDPKTGVEFKDTLISPET GVKARIVLPKINGPDHKLPLLVHYHGGGFCMGSSLDTVTLRFLTSLASQA HLIAISVDYRLAPEHPLPIAYEDSWSALQWIATHSNGQGPDPWLNQYADF GRVFLAGESAGANIAHQVAVRVGTVGLEGFMPRGVIIIHPYFAGSEPDKM IQYLYPGSSGSEDDPNLSPKEDPNLTKMGCSKVIVFVAEKDRLKPRGVDY YETLKNSGWEGRVEFVEDKGEDHCFHMFSPNSDKVVGLMQKLGTFVNEN
Plant tannases (TAs) or tannin acyl hydrolases, a class of recently reported carboxylesterase (CXE) in tannin-rich plants, are involved in the degalloylation of two important secondary metabolites: flavan-3-ol gallates and hydrolyzable tannins (HTs). In this paper, we have made a new progress on the function of Camellia sinensis (Cs) TA-it is a hydrolase with promiscuous acyltransferase activity in vitro and in vivo experiments and promotes the synthesis of simple galloyl glucoses and flavan-3-ols gallates in plants. We gained the new understanding to the functions of CsTA through enzyme analysis, protein mass spectrometry identification, metabolic analysis of plants by genetic modification. Firstly, CsTA was proved that it is not only a hydrolase but also an acyltransferase. In the two-step covalent catalytic reaction, when CsTA hydrolyzes the galloylated compounds epigallocatechin-3-gallate (EGCG) or 1,2,3,4,6-penta-O-galloyl-beta-D-glucose (PGG) into their degalloylated forms, a long-lived Ser159-linked galloyl-enzyme covalent intermediate is also formed. Under nucleophilic attack, the galloyl group on the intermediate is transferred to the nucleophilic acyl acceptors (including water, methanol, flavan-3-ols and simple galloyl glucoses). Then, metabolic analysis suggested that transiently overexpression of TAs in young strawberry fruits, young leaves of tea plants and young leaves of Chinese bayberry actually increased the total content of simple galloyl glucoses and flavan-3-ol gallates. Overall, these findings provide new insights into the promiscuous acyltransferase activity of plant tannase.
Tannins are important polyphenol compounds with different component proportions in different plant species. The plants in the Juglandaceae are rich in tannins, including condensed tannins and hydrolyzable tannins. In this study, we identified seven tannase genes (TAs) responsible for the tannin metabolism from walnut, pecan, and Chinese hickory, and three nut tree species in the Juglandaceae, which were divided into two groups. The phylogenetic and sequence analysis showed that TA genes and neighboring clade genes (TA-like genes) had similar sequences compared with other carboxylesterase genes, which may be the origin of TA genes produced by tandem repeat. TA genes also indicated higher expressions in leaf than other tissues and were quickly up-regulated at 3 h after leaf injury. During the development of the seed coat, the expression of the synthesis-related gene GGTs and the hydrolase gene TAs was continuously decreased, resulting in the decrease of tannin content in the dry sample of the seed coat of Chinese hickory. However, due to the reduction in water content during the ripening process, the tannin content in fresh sample increased, so the astringent taste was obvious at the mature stage. In addition, the CcGGTs' expression was higher than CiGGTs in the initiation of development, but CcTAs continued to be down-regulated while CiTA2a and CiTA2b were up-regulated, which may bring about the significant differences in tannin content and astringent taste between Chinese hickory and pecan. These results suggested the crucial role of TAs in wound stress of leaves and astringent ingredient accumulation in seed coats of two nut tree species in the Juglandaceae.
Plant tannins, including condensed tannins (CTs) and hydrolyzable tannins (HTs), are widely distributed in the plant kingdom. To date, tannase (TA) - is a type of tannin acyl-hydrolase hydrolyzing HTs, CT monomer gallates and depsides - has been reported in microbes only. Whether plants express TA remains unknown. Herein, we report plant TA genes. A native Camellia sinensis TA (CsTA) is identified from leaves. Six TAs are cloned from tea, strawberry (Fragariasxsananassa, Fa) and four other crops. Biochemical analysis shows that the native CsTA and six recombinant TAs hydrolyze tannin compounds, depsides and phenolic glycosides. Transcriptional and metabolic analyses reveal that the expression of CsTA is oppositely associated with the accumulation of galloylated catechins. Moreover, the transient overexpression and RNA interference of FaTA are positively associated with the accumulation of ellagitannins in strawberry fruit. Phylogenetic analysis across different kingdoms shows that 29 plant TA homologs are clustered as a plant-specific TA clade in class I carboxylesterases. Further analysis across the angiosperms reveals that these TA genes are dispersed in tannin-rich plants, which share a single phylogenetic origin c. 120 million yr ago. Plant TA is discovered for the first time in the plant kingdom and is shown to be valuable to improve tannin compositions in plants.
