3 research outputs found
Biosynthesis of Jasmine Lactone in Tea (<i>Camellia sinensis</i>) Leaves and Its Formation in Response to Multiple Stresses
Jasmine lactone has a potent odor
that contributes to the fruity,
sweet floral aroma of tea (<i>Camellia sinensis</i>). Our
previous study demonstrated that jasmine lactone was mostly accumulated
at the turnover stage of the oolong tea manufacturing process. This
study investigates the previously unknown mechanism of formation of
jasmine lactone in tea leaves exposed to multiple stresses occurring
during the growth and manufacturing processes. Both continuous mechanical
damage and the dual stress of low temperature and mechanical damage
enhanced jasmine lactone accumulation in tea leaves. In addition,
only one pathway, via hydroperoxy fatty acids from unsaturated fatty
acid, including linoleic acid and α-linolenic acid, under the
action of lipoxygenases (LOXs), especially CsLOX1, was significantly
affected by these stresses. This is the first evidence of the mechanism
of jasmine lactone formation in tea leaves and is a characteristic
example of plant volatile formation in response to dual stress
Biosynthetic Pathway and Bioactivity of Vanillin, a Highly Abundant Metabolite Distributed in the Root Cortex of Tea Plants (<i>Camellia sinensis</i>)
Volatiles are important for plant root stress resistance.
The diseases
in tea root are serious, causing major losses. The volatile composition
in tea root and whether it can resist diseases remain unclear. In
this study, the volatile composition in different tea tissues was
revealed. The vanillin content was higher in the root (mainly in root
cortex) than in aerial parts. The antifungal effects of vanillin on
pathogenic fungi in tea root were equal to or greater than those of
other metabolites. O-methyltransferase (CsOMT), a
key enzyme in one of two biosynthetic pathways of vanillin, converted
protocatechualdehyde to vanillin in vitro. Furthermore,
its characteristics and kinetic parameters were studied. In Arabidopsis thaliana protoplasts, the transiently
expressed CsOMT was localized in the cytoplasm and nucleus. These
findings have clarified the formation and bioactivities of volatiles
in tea roots and provided a theoretical basis for understanding how
tea plants resist root diseases
Formation of Volatile Tea Constituent Indole During the Oolong Tea Manufacturing Process
Indole is a characteristic
volatile constituent in oolong tea.
Our previous study indicated that indole was mostly accumulated at
the turn over stage of oolong tea manufacturing process. However,
formation of indole in tea leaves remains unknown. In this study,
one tryptophan synthase α-subunit (TSA) and three tryptophan
synthase β-subunits (TSBs) from tea leaves were isolated, cloned,
sequenced, and functionally characterized. Combination of CsTSA and
CsTSB2 recombinant protein produced in <i>Escherichia coli</i> exhibited the ability of transformation from indole-3-glycerol phosphate
to indole. CsTSB2 was highly expressed during the turn over process
of oolong tea. Continuous mechanical damage, simulating the turn over
process, significantly enhanced the expression level of CsTSB2 and
amount of indole. These suggested that accumulation of indole in oolong
tea was due to the activation of CsTSB2 by continuous wounding stress
from the turn over process. Black teas contain much less indole, although
wounding stress is also involved in the manufacturing process. Stable
isotope labeling indicated that tea leaf cell disruption from the
rolling process of black tea did not lead to the conversion of indole,
but terminated the synthesis of indole. Our study provided evidence
concerning formation of indole in tea leaves for the first time