Acyl-Acyl Carrier Protein Desaturases and Plant Biotic Interactions.

Sami Kazaz,Romane Miray,Sébastien Baud

doi:10.3390/cells10030674

Abstract

Interactions between land plants and other organisms such as pathogens, pollinators, or symbionts usually involve a variety of specialized effectors participating in complex cross-talks between organisms. Fatty acids and their lipid derivatives play important roles in these biological interactions. While the transcriptional regulation of genes encoding acyl–acyl carrier protein (ACP) desaturases appears to be largely responsive to biotic stress, the different monounsaturated fatty acids produced by these enzymes were shown to take active part in plant biotic interactions and were assigned with specific functions intrinsically linked to the position of the carbon–carbon double bond within their acyl chain. For example, oleic acid, an omega-9 monounsaturated fatty acid produced by Δ9-stearoyl–ACP desaturases, participates in signal transduction pathways affecting plant immunity against pathogen infection. Myristoleic acid, an omega-5 monounsaturated fatty acid produced by Δ9-myristoyl–ACP desaturases, serves as a precursor for the biosynthesis of omega-5 anacardic acids that are active biocides against pests. Finally, different types of monounsaturated fatty acids synthesized in the labellum of orchids are used for the production of a variety of alkenes participating in the chemistry of sexual deception, hence favoring plant pollination by hymenopterans.

Highlights

In plant cells, fatty acids produced in the plastids are used for the biosynthesis of a variety of lipid compounds
Aside from this, some fatty acids, acyl lipids, and their derivatives participate in signal transduction pathways that influence plant development and responses to environmental cues [5,6]
Before and concurrent with the onset of PAMP-triggered immunity (PTI), changes in membrane lipid composition and adjustment of membrane fluidity largely mediated by desaturases appear to be critical for the function of integral membrane proteins that participate in this response [11,12]

Summary

Introduction

Fatty acids produced in the plastids are used for the biosynthesis of a variety of lipid compounds. ∆9-Stearoyl–ACP desaturases represent the predominant AAD isoforms in most land plants They efficiently desaturate 18:0 (stearic acid) to form ω-9 18:1, a major monounsaturated fatty acid of membrane and storage lipids [27]. The structural basis for the different chain-length and double bond positional specificities of AADs were identified through the characterization of desaturases exhibiting different functional properties despite sharing high amino acid sequence similarity [42]. In this respect, approaches of site-directed mutagenesis aimed at converting the activity of one type of AAD to that of another by replacing specific residues have been proven to be very informative [43]. Determination of crystal structures of AADs in complex with acyl-ACPs identified residues at the entrance of the substrate-binding cavity that are determinants for the binding modes of ACP with respect to the desaturase, predisposing the potential insertion depth of the acyl chain and thereby influencing regioselectivity [44]

Transcriptional Responses of AAD Genes to Biotic Stress in Arabidopsis Leaves

Synthesis of ω-Anacardic Acids and Resistance to Pests in Geranium

Findings

Synthesis of Alkenes and Attraction of Pollinators in Orchids