Introduction
Colour transformation and volatiles emitting both contribute to tomato
quality, they are often accompanied with each other. Moreover, both the
carotenoids and green leaf volatile (GLVs) are synthesized in the
plastids (Barr, White, Chen, Bae &
Rodermel, 2004, Bonaventure, Schuck &
Baldwin, 2011). In this study we are trying to establish a regulatory
relationship between colour transformation and volatiles emitting.
Before the inner membrane structures (IMS) of chloroplasts
transformation, carotenoids synthesis has started in grana and stroma
thylakoids and then packed into IMS
(Schweiggert, Steingass, Heller, Esquivel
& Carle, 2011, Sun, Yuan, Cao, Yazdani,
Tadmor & Li, 2018). The chromoplast characteristic structures
including tubular elements (te), plastoglobules (pg) and crystal
remnants (cr) have been reported to be induced by the early accumulated
carotenoids (Lu, Wang, Yin, Zhong,
Grierson, Chen & Xu, 2017, Schweiggertet al. , 2011). Howerver, the mechanism of the carotenoids
started IMS transformation in the chloroplasts still remains unclear
(Sun & Li, 2020).
Based on our research, one of the GLVs, E -2-hexenal (E2H) may
function downstream of carotenoids to regulate the transformation. E2H
is one of the most abundant volatiles in fruits including tomato
(Hammerbacher, Coutinho & Gershenzon,
2019). The biosynthesis of E2H consume the membrane lipids and
energies, therefore the function of E2H must be beneficial to survival
(Mumm, Posthumus & Dicke, 2008). Most
plants, including single-cell algae, have evolved the E2H synthesis and
release mechanisms (Ma, Xiao, Li, Li, Shi,
Liang, Lu & Chen, 2011). But according to the theory of evolution,
algae did not seem to use E2H as allelopathic molecules to react with
biotic stress signals because biotic stress didn’t exist then. Different
from the allergic effects previously reported, E2H is proposed to
involve in the regulation of tomato colour transformation in this study.
In this study, we tried to verify the hypothesis that E2H play critical
role in activating the IMS transformation in chloroplasts.