Abstract
The phenylpropanoid and flavonoid families include thousands of specialized metabolites that influence a wide range of processes in plants, including seed dispersal, auxin transport, photoprotection, mechanical support and protection against insect herbivory. Such metabolites play a key role in the protection of plants against abiotic stress, in many cases through their well-known ability to inhibit the formation of reactive oxygen species (ROS). However, the precise role of specific phenylpropanoid and flavonoid molecules is unclear. We therefore investigated the role of specific anthocyanins (ACs) and other phenylpropanoids that accumulate in carrot cells cultivated in vitro, focusing on their supposed ability to protect cells from heat stress. First we characterized the effects of heat stress to identify quantifiable morphological traits as markers of heat stress susceptibility. We then fed the cultures with precursors to induce the targeted accumulation of specific compounds, and compared the impact of heat stress in these cultures and unfed controls. Data modeling based on projection to latent structures (PLS) regression revealed that metabolites containing coumaric or caffeic acid, including ACs, correlate with less heat damage. Further experiments suggested that one of the cellular targets damaged by heat stress and protected by these metabolites is the actin microfilament cytoskeleton.
Highlights
Phenylpropanoids and flavonoids are two important classes of plant phenolic specialized metabolites widely distributed in plant kingdom
The precise biological role of specific specialized metabolites can be challenging to define because it is difficult to establish biological systems that differ solely in the content of individual molecules. This reflects the ability of plant cells to accumulate diverse metabolites by the decoration of a smaller number of basic structures, but the precise meaning of the existence of this plethora of different decorations in vivo as well as how they are genetically regulated and obtained is poorly understood
Carrot cells accumulate non-acylated ACs and ACs acylated with coumaric, caffeic, ferulic, and sinapic acids
Summary
Phenylpropanoids and flavonoids are two important classes of plant phenolic specialized metabolites widely distributed in plant kingdom. In the phenylpropanoid and flavonoid families, the basic structures are often converted into glycosylated derivatives, esters with both aliphatic and aromatic organic acids, and amides with nitrogen-containing metabolites such as aminoacids and polyamines (Dixon and Paiva, 1995; Macoy et al, 2015) These decorations confer different physicochemical properties that have been investigated and partially elucidated in vitro. In the case of ACs, which is a sub-class of flavonoids, glycosylation results in redder pigmentation, aromatic acylation (usually with HBAs and HCAs) results in a blue shift and greater molecular stability, and aliphatic acylation increases molecular stability and solubility (Tanaka et al, 2008) The implications of these different modifications in vivo is not well understood, and little is known about their involvement in specific biological functions
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