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.