Terpenoid Transport in Plants: How Far from the Final Picture?

Abstract

Contrary to the biosynthetic pathways of many terpenoids, which are well characterized and elucidated, their transport inside subcellular compartments and the secretion of reaction intermediates and final products at the short- (cell-to-cell), medium- (tissue-to-tissue), and long-distance (organ-to-organ) levels are still poorly understood, with some limited exceptions. In this review, we aim to describe the state of the art of the transport of several terpene classes that have important physiological and ecological roles or that represent high-value bioactive molecules. Among the tens of thousands of terpenoids identified in the plant kingdom, only less than 20 have been characterized from the point of view of their transport and localization. Most terpenoids are secreted in the apoplast or stored in the vacuoles by the action of ATP-binding cassette (ABC) transporters. However, little information is available regarding the movement of terpenoid biosynthetic intermediates from plastids and the endoplasmic reticulum to the cytosol. Through a description of the transport mechanisms of cytosol- or plastid-synthesized terpenes, we attempt to provide some hypotheses, suggestions, and general schemes about the trafficking of different substrates, intermediates, and final products, which might help develop novel strategies and approaches to allow for the future identification of terpenoid transporters that are still uncharacterized.

Production of Saffron Apocarotenoids in Nicotiana benthamiana Plants Genome-Edited to Accumulate Zeaxanthin Precursor

“…This hypothesis could be tested by transcriptomic analyses of TEV:CsCCD2-infected plants in comparison with an empty vector control. Another factor contributing to accumulation of crocins is their sequestration into va uoles [7,40]. Co-agroinfiltration of the CsABCC4a transporter in N. benthamiana leaves t gether with CsCCD2 increases the levels of crocins, indicating that endogenous vacuol transport in N. benthamiana leaves may be rate-limiting for crocin accumulation [7].…”

From Plants to Wound Dressing and Transdermal Delivery of Bioactive Compounds

“…This class of SM basically consists of five carbon isoprene units, assembled to each other (many isoprene units) in thousands of ways. Terpenes are simple hydrocarbons, while terpenoids are a modified class of terpenes, with isopentenyl pyrophosphate (IPP) as a structural unit, with different functional groups and an oxidized methyl group moved or removed at various positions [ 221 ].…”

Research Progress in Heterologous Crocin Production

“…The crocin biosynthesis pathway in C. sativus, from zeaxanthin to the crocins themselves, lies downstream of the methylerythritol phosphate (MEP) and mevalonate (MVA) pathways, which supply precursors and metabolites to the midstream carotenoid pathway, comprising GGPP to zeaxanthin (Figure 2) [14,[70][71][72][73][74][75][76][77][78][79][80][81][82][83][84]. Apart from the astaxanthin synthesis pathway, which is only present in a few specialized microalgae, most algal species in the taxon Chlorophyta share the majority of steps in the carotenoid biosynthesis pathway with higher plants [85].…”