Plant Fatty Acid Research Articles

Resolving Free-Energy Contributions of Substrate Delivery to Desaturase by Atomistic Simulations

The plant acyl-acyl carrier protein (ACP) desaturases are a family of soluble enzymes that convert saturated fatty-acyl ACPs into their cis-monounsaturated equivalents in an oxygen-dependent reaction. These enzymes play a key role in biosynthesis of mono-unsaturated fatty acids in plants. The archetype of this group is the ▵9-18:0-ACP desaturase that introduces a cis double bond between carbons 9 and 10 to produce oleoyl-ACP. ACPs are central proteins in the fatty acid biosynthesis that deliver the substrate to the desaturase. They have been reported to show a varying degree of local dynamics and structural variability depending on the substrate length. It has been suggested that the substrate specific change in structure and dynamics is crucial for the decreasing enzymatic activity in the case of the ▵9-desaturase for chains length shorter than 18. We investigated the solution structure and dynamics of ACP with four different substrate lengths (10, 14, 16, and 18) based on published NMR solution structures using extensive all atom molecular dynamics simulations. Umbrella sampling and replica exchange dynamics simulations highlight the chain length depend free energy of substrate binding and chain length depended binding motifs. This suggests that longer substrates have a lower binding energy, but also a much larger ensemble of structures that are accessible. Thereby estimating the effect on changes in the binding affinity of the substrate bound Acyl carrier protein to the ▵9-desaturase will not be able without taking into account the Enzyme itself.

Glycerol-Induced Powdery Mildew Resistance in Wheat by Regulating Plant Fatty Acid Metabolism, Plant Hormones Cross-Talk, and Pathogenesis-Related Genes.

Our previous study indicated that glycerol application induced resistance to powdery mildew (Bgt) in wheat by regulating two important signal molecules, glycerol-3-phosphate (G3P) and oleic acid (OA18:1). Transcriptome analysis of wheat leaves treated by glycerol and inoculated with Bgt was performed to identify the activated immune response pathways. We identified a set of differentially expressed transcripts (e.g., TaGLI1, TaACT1, and TaSSI2) involved in glycerol and fatty acid metabolism that were upregulated in response to Bgt infection and might contribute to G3P and OA18:1 accumulation. Gene Ontology (GO) enrichment analysis revealed GO terms induced by glycerol, such as response to jasmonic acid (JA), defense response to bacterium, lipid oxidation, and growth. In addition, glycerol application induced genes (e.g., LOX, AOS, and OPRs) involved in the metabolism pathway of linolenic and alpha-linolenic acid, which are precursor molecules of JA biosynthesis. Glycerol induced JA and salicylic acid (SA) levels, while glycerol reduced the auxin (IAA) level in wheat. Glycerol treatment also induced pathogenesis related (PR) genes, including PR-1, PR-3, PR-10, callose synthase, PRMS, RPM1, peroxidase, HSP70, HSP90, etc. These results indicate that glycerol treatment regulates fatty acid metabolism and hormones cross-talk and induces the expression of PR genes that together contribute to Bgt resistance in wheat.

A Pathogen-Responsive Gene Cluster for Highly Modified Fatty Acids in Tomato

In response to biotic stress, plants produce suites of highly modified fatty acids that bear unusual chemical functionalities. Despite their chemical complexity and proposed roles in pathogen defense, little is known about the biosynthesis of decorated fatty acids in plants. Falcarindiol is a prototypical acetylenic lipid present in carrot, tomato, and celery that inhibits growth of fungi and human cancer cell lines. Using a combination of untargeted metabolomics and RNA sequencing, we discovered a biosynthetic gene cluster in tomato (Solanum lycopersicum) required for falcarindiol production. By reconstituting initial biosynthetic steps in a heterologous host and generating transgenic pathway mutants in tomato, we demonstrate a direct role of the cluster in falcarindiol biosynthesis and resistance to fungal and bacterial pathogens in tomato leaves. This work reveals a mechanism by which plants sculpt their lipid pool in response to pathogens and provides critical insight into the complex biochemistry of alkynyl lipid production.

Development of a rice herbicide, fenoxasulfone.

Fenoxasulfone is a novel rice herbicide that was discovered and developed by Kumiai Chemical Industry Co., Ltd. It displays excellent herbicidal activity against Echinochloa spp. and other annual weeds at 150–200 g a.i./ha with long residual activity and has a favorable toxicological, ecotoxicological, and environmental profile. Fenoxasulfone’s mode of action was investigated, and it has been shown to inhibit the biosynthesis of very-long-chain fatty acids in plants. Fenoxasulfone was registered in Japan in 2014, and various products containing fenoxasulfone have been launched. With its high efficacy and long residual activity, we believe that fenoxasulfone will contribute to efficient food production in the future.

Cloning and functional analysis of the FAD2 gene family from desert shrub Artemisia sphaerocephala

BackgroundLinoleic acid is an important polyunsaturated fatty acid, required for all eukaryotes. Microsomal delta-12 (Δ12) oleate desaturase (FAD2) is a key enzyme for linoleic acid biosynthesis. Desert shrub Artemisia sphaerocephala is rich in linoleic acid, it has a large FAD2 gene family with twenty-six members. The aim of this work is to unveil the difference and potentially functionality of AsFAD2 family members.ResultsFull-length cDNAs of twenty-one AsFAD2 genes were obtained from A. sphaerocephala. The putative polypeptides encoded by AsFAD2 family genes showed a high level of sequence similarity and were relatively conserved during evolution. The motif composition was also relatively conservative. Quantitative real-time PCR analysis revealed that the AsFAD2–1 gene was strongly expressed in developing seeds, which may be closely associated with the high accumulating ability of linoleic acid in A. sphaerocephala seeds. Although different AsFAD2 family members showed diverse response to salt stress, the overall mRNA levels of the AsFAD2 family genes was stable. Transient expression of AsFAD2 genes in the Nicotiana benthamiana leaves revealed that the encoded proteins were all located in the endoplasmic reticulum. Heterologous expression in Saccharomyces cerevisiae suggested that only three AsFAD2 enzymes, AsFAD2–1, − 10, and − 23, were Δ12 oleate desaturases, which could convert oleic acid to linoleic acid, whereas AsFAD2–1 and AsFAD2–10 could also produce palmitolinoleic acid.ConclusionsThis research reported the cloning, expression studies, subcellular localization and functional identification of the large AsFAD2 gene family. These results should be helpful in understanding fatty acid biosynthesis in A. sphaerocephala, and has the potential to be applied in the study of plant fatty acids traits.

Proximate and phenolic composition of selected native Australian food plants

SummaryEdible portions of Leucopogon parviflorus, Arthropodium strictum, Carpobrotus rossii, Rhagodia candolleana, Typha orientalis, Correa alba, Dianella revoluta and Acacia longifolia were collected in 2017 and 2019 from Warrnambool, Victoria Australia, and studied for phenolics and proximate composition. The plant species recorded consistent antioxidant activity with no nutritional alterations. Except for A. longifolia, total phenolic contents (TPC) were higher in 2019 than 2017 (P < 0.05). All the plant species contained Ca, Mg, Na and K. Except for betanin, isolated from R. candolleana (700 mg L−1) and C. rossii (244 mg L−1), higher quantities of polyphenols were extractable in methanol than water (P < 0.05). The plant fatty acid composition was predominantly palmitic, oleic and linoleic acids with A. longifolia containing 44% linoleic acid. While the plant nutrients and fatty acids were fairly stable, TPCs, some of the minerals and polyphenols varied between the years.

Enantioselective Phytotoxic Disturbances of Fatty Acids in Arabidopsis thaliana by Dichlorprop.

Plant fatty acids have indispensable physiological functions and nutritional value. However, the overuse of herbicides may cause phytotoxic disturbances of fatty acids in nontarget plants while spraying for weeds. Evidence has shown that the herbicide dichlorprop can inhibit the activity of acetyl-CoA carboxylase (ACCase), a key enzyme involved in fatty acid synthesis. However, the enantioselective phytotoxic effects of dichlorprop enantiomers ((R)-dichlorprop and (S)-dichlorprop) on fatty acids and their related mechanisms remain unclear. To solve this issue, the enantioselective phytotoxicity of dichlorprop in the model plant species Arabidopsis thaliana (A. thaliana) with a focus on fatty acids was evaluated for the first time. The results indicated a significant difference in enantioselectivity and that exposure to (R)-dichlorprop can cause marked fatty acid disturbances in nontarget plant species. Specifically, (R)-dichlorprop decreased the content of three fatty acids by more than 50% by inhibiting the activity of ACCase. In addition, increased malondialdehyde (MDA) and lipid hydroperoxides (LOOHs) contents and membrane permeability reflected herbicide-induced lipid peroxidation, which decreased the unsaturation of fatty acids in membranes and further influenced membrane composition and function. Moreover, an increased level of glutathione peroxidase (GPX) and cytochrome P450 (CYP450) reflected a plant stress-induced response. To summarize, fatty acids represent a new perspective for evaluating the toxicity of chiral pesticides, contributing to a better understanding of the enantioselective phytotoxicity and mechanisms of dichlorprop, and providing evidence for herbicide security and risk assessments.

Identification of Fatty Acid Desaturases in Maize and Their Differential Responses to Low and High Temperature.

Plant fatty acid desaturases (FADs) catalyze the desaturation of fatty acids in various forms and play important roles in regulating fatty acid composition and maintaining membrane fluidity under temperature stress. A total of 30 FADs were identified from a maize genome, including 13 soluble and 17 membrane-bound FADs, which were further classified into two and five sub-groups, respectively, via phylogenetic analysis. Although there is no evolutionary relationship between the soluble and the membrane-bound FADs, they all harbor a highly conserved FA_desaturase domain, and the types and the distributions of conserved motifs are similar within each sub-group. The transcriptome analysis revealed that genes encoding FADs exhibited different expression profiles under cold and heat stresses. The expression of ZmFAD2.1&2.2, ZmFAD7, and ZmSLD1&3 were significantly up-regulated under cold stress; moreover, the expression of ZmFAD2.1&2.3 and ZmSLD1&3 were obviously down-regulated under heat stress. The co-expression analysis demonstrated close correlation among the transcription factors and the significant responsive FAD genes under cold or heat stress. This study helps to understand the roles of plant FADs in temperature stress responses.

Trophic importance of microphytobenthos and bacteria to meiofauna in soft-bottom intertidal habitats: A combined trophic marker approach

Meiofauna can play an important role in the carbon fluxes of soft-bottom coastal habitats. Investigation of their feeding behavior and trophic position remains challenging due to their small size. In this study, we determine and compare the food sources used by nematodes and benthic copepods by using stable isotope compositions, fatty acid profiles and compound specific isotope analyses of fatty acids in the mudflats, seagrass beds and a sandflat of the Marennes-Oléron Bay, France, and the Sylt-Rømø Bight, Germany. Suspended particulate organic matter was much more 13C-depleted than other food sources and meiofauna, highlighting its poor role in the different studied habitats. The very low proportions of vascular plant fatty acid markers in meiofauna demonstrated that these consumers did not rely on this food source, either fresh or detrital, even in seagrass beds. The combined use of stable isotopes and fatty acids emphasized microphytobenthos and benthic bacteria as the major food sources of nematodes and benthic copepods. Compound specific analyses of a bacteria marker confirmed that bacteria mostly used microphytobenthos as a substrate.

Linoleic acid, a plant fatty acid, controls membrane biofouling via inhibition of biofilm formation

Biofouling of reverse osmosis (RO) membranes increases the operation cost of the seawater desalination process, by reducing salt rejection and increasing permeation pressure. However, biocides commonly used to inhibit biofouling not only increase bacterial resistance, but also damage the chemical structure of the RO membrane due to oxidation. Linoleic acid (LA), a polyunsaturated fatty acid, inhibits biofilm formation by Pseudomonas aeruginosa, without affecting bacterial growth. After treatment with LA, the volume and thickness of biofilm on the RO membrane decreased by 47% and 33%, respectively, without affecting the morphology and chemical structure of the RO membranes. Based on these results, LA was applied to control the biofouling in a laboratory-scale RO system. Upon treatment with LA, a loose and porous biofilm formed on the RO membrane, which demonstrated increased membrane performance and water permeability when compared with untreated system. These results suggest that LA can be used as a biofouling inhibitor in RO processes.

Structural analysis of a plant fatty acid amide hydrolase provides insights into the evolutionary diversity of bioactive acylethanolamides

N-Acylethanolamines (NAEs) are fatty acid derivatives that in animal systems include the well-known bioactive metabolites of the endocannabinoid signaling pathway. Plants use NAE signaling as well, and these bioactive molecules often have oxygenated acyl moieties. Here, we report the three-dimensional crystal structures of the signal-terminating enzyme fatty acid amide hydrolase (FAAH) from Arabidopsis in its apo and ligand-bound forms at 2.1- and 3.2-Å resolutions, respectively. This plant FAAH structure revealed features distinct from those of the only other available FAAH structure (rat). The structures disclosed that although catalytic residues are conserved with the mammalian enzyme, AtFAAH has a more open substrate-binding pocket that is partially lined with polar residues. Fundamental differences in the organization of the membrane-binding "cap" and the membrane access channel also were evident. In accordance with the observed structural features of the substrate-binding pocket, kinetic analysis showed that AtFAAH efficiently uses both unsubstituted and oxygenated acylethanolamides as substrates. Moreover, comparison of the apo and ligand-bound AtFAAH structures identified three discrete sets of conformational changes that accompany ligand binding, suggesting a unique "squeeze and lock" substrate-binding mechanism. Using molecular dynamics simulations, we evaluated these conformational changes further and noted a partial unfolding of a random-coil helix within the region 531-537 in the apo structure but not in the ligand-bound form, indicating that this region likely confers plasticity to the substrate-binding pocket. We conclude that the structural divergence in bioactive acylethanolamides in plants is reflected in part in the structural and functional properties of plant FAAHs.

In-silico study of flavonoids from Cassia tora as potential anti-psoriatic agent

Psoriasis is a skin disease that affect 2-3 % of the world’s population. As a shift from the popular focus on plant fatty acid, fifteen flavonoids from Cassia tora were evaluated in-silico for their ability to bind to fifteen anti-psoriatic targets. It was observed that all the flavonoids made varying degrees of favourable binding interactions with each of the protein targets. London dG scoring method identified that five compounds had higher binding affinity toward TNF-α, BTK, PAD and SPK than their co-crystallized ligands. Twelve of the flavonoids made better binding interactions with AA2R, PK and PKC than their co-crystallized inhibitors whereas all the compounds except 6 had lower free binding energy toward P38MK, IL-17A, PDE-4, CCS and Jak-3 than their native ligands. Only the docking scores of three molecules (1, 2 and 8) ranked lower than the reference ligands of S1PR and Rac1. Moreover, it was noted that only 2 interacted with IL-23 with binding affinity comparable to its native ligand. The docking scores of the studied flavonoids highlight the presence of highly polar group (especially sugar) as a vital structural requirement for strong binding with the target proteins.

Functional characterization and structural modelling of Helianthus annuus (sunflower) ketoacyl-CoA synthases and their role in seed oil composition.

The enzymes HaKCS1 and HaKCS2 are expressed in sunflower seeds and contribute to elongation of C18 fatty acids, resulting in the C20-C24 fatty acids in sunflower oil. Most plant fatty acids are produced by plastidial soluble fatty acid synthases that produce fatty acids of up to 18 carbon atoms. However, further acyl chain elongations can take place in the endoplasmic reticulum, catalysed by membrane-bound synthases that act on acyl-CoAs. The condensing enzymes of these complexes are the ketoacyl-CoA synthase (KCSs), responsible for the synthesis of very long chain fatty acids (VLCFAs) and their derivatives in plants, these including waxes and cuticle hydrocarbons, as well as fatty aldehydes. Sunflower seeds accumulate oil that contains around 2-3% of VLCFAs and studies of the fatty acid elongase activity in developing sunflower embryos indicate that two different KCS isoforms drive the synthesis of these fatty acids. Here, two cDNAs encoding distinct KCSs were amplified from RNAs extracted from developing sunflower embryos and named HaKCS1 and HaKCS2. These genes are expressed in developing seeds during the period of oil accumulation and they are clear candidates to condition sunflower oil synthesis. These two KCS cDNAs complement a yeast elongase null mutant and when expressed in yeast, they alter the host's fatty acid profile, proving the encoded KCSs are functional. The structure of these enzymes was modelled and their contribution to the presence of VLCFAs in sunflower oil is discussed based on the results obtained.

Characteristics of membrane-bound fatty acid desaturase (FAD) genes in Brassica napus L. and their expressions under different cadmium and salinity stresses

The membrane-bound fatty acid desaturases (FADs) play vital roles in regulating plant fatty acid (FA) compositions which directly affect oil quality in rapeseed (Brassica napus L.). In the present study, a total of 68 putative FAD genes were identified in the crop and were phylogenetically clustered into four subfamilies. Genomic localization revealed that the genes were distributed across 21 chromosomes at various densities. The structures of paralogous genes were considerably conserved in the number of exons and in the length of introns. It was found that the expansion of the B. napus FAD family was mainly attributable to whole genome duplication and segmental duplication. Rapeseed seedlings were grown hydroponically under three levels (0, 250, and 500 μM) of cadmium (Cd) and three levels (0, 50, and 100 mM) of salinity. After one week of treatment, the roots and leaves of seedlings were harvested to study the expression patterns of 68 selected BnFADs in response to the different stresses. The results from qRT-PCR analyses suggested that the FAD genes in rapeseed were differentially expressed under various abiotic stresses. The transcript levels of the FAD genes ADS4.8, ADS4.9, ADS4.10, ADS9.1 and SLD8 in the leaves of Cd-tolerant cultivar ZD619 were significantly higher than those in the leaves of sensitive cultivar ZD622 under the 250 μM Cd stress condition. Moreover, the expression levels of 8FAD genes (ADS4.1, ADS4.4, ADS4.9, ADS9.1, ADS9.2, SLD8, FAD7.4 and FAD7.5) in ZD619 roots were obviously enhanced with the increase of salinity concentrations. These results indicate the likelihood of FAD genes involved in Cd and salinity tolerance. This study provides insight on membrane-bound FAD genes involvement in tolerance to abiotic stresses and would provide some more candidate genes for the crop improvement.

Detection of Divinyl Ether Synthase Activity and a Novel Oxylipin (1'Z)–Colneleic Acid in Asparagus (Asparagus officinalis L.)

The activity of divinyl ether synthase (EC: 4.2.1.121), an enzyme involved in the lipoxygenase cascade of unsaturated fatty acids in plants, has been found in the roots and stalks of asparagus Asparagus officinalis L. Incubation of homogenates of roots and/or etiolated stalks of Asparagus officinalis L. with linoleic acid results in the formation of mainly divinyl ether (9Z,11Z,1'E)-12-(1'-hexenyloxy)-9,11-dodecadienoic acid ((11Z)-etheroleic acid), as well as a minor amount of its geometric isomer (9Z,11E,1'E)-12-(1'-hexenyloxy)-9,11-dodecadienoic acid (etheroleic acid). These compounds are derived from linoleic acid by the sequential action of regiospecific 13-lipoxygenase and divinyl ether synthase. Moreover, a minor compound, whose amount increases after the incubation of homogenates with the 9-hydroperoxide of linoleic acid ((9S,10E,12Z)-9-hydroperoxy(10,12)–octadecadienoic acid), has been found. This compound has been identified as (8E,1'Z,3'Z)-9-(1',3'-nonadienyloxy)-8-nonenoic acid ((1'Z)-colneleic acid). These data suggest that nonphotosynthetic tissues of asparagus exhibit the activity of a novel 13/9-specific divinyl ether synthase.

PlantFAdb: a resource for exploring hundreds of plant fatty acid structures synthesized by thousands of plants and their phylogenetic relationships.

Over 450 structurally distinct fatty acids are synthesized by plants. We have developed PlantFAdb.org, an internet-based database that allows users to search and display fatty acid composition data for over 9000 plants. PlantFAdb includes more than 17000 data tables from >3000 publications and hundreds of unpublished analyses. This unique feature allows users to easily explore chemotaxonomic relationships between fatty acid structures and plant species by displaying these relationships on dynamic phylogenetic trees. Users can navigate between order, family, genus and species by clicking on nodes in the tree. The weight percentage of a selected fatty acid is indicated on phylogenetic trees and clicking in the graph leads to underlying data tables and publications. The display of chemotaxonomy allows users to quickly explore the diversity of plant species that produce each fatty acid and that can provide insights into the evolution of biosynthetic pathways. Fatty acid compositions and other parameters from each plant species have also been compiled from multiple publications on a single page in graphical form. Links provide simple and intuitive navigation between fatty acid structures, plant species, data tables and the publications that underlie the datasets. In addition to providing an introduction to this resource, this report illustrates examples of insights that can be derived from PlantFAdb. Based on the number of plant families and orders that have not yet been surveyed we estimate that a large number of novel fatty acid structures are still to be discovered in plants.

Functional characterization of a Δ6 fatty acid desaturase gene and its 5′-upstream region cloned from the arachidonic acidrich microalga Myrmecia incisa Reisigl (Chlorophyta)

It is suggested that Δ6 fatty acid desaturase (FAD) plays a critical role in the biosynthesis of polyunsaturated fatty acids in plants and microalgae. But why does it adapt to the changed environments such as nitrogen starvation is seldom understood. One Δ6 FAD gene ( MiD6fad ) from an arachidonic acidrich microalga Myrmecia incisa Reisigl (Chlorophyta) was first heterologously expressed in Saccharomyces cerevisiae for the identification of function. The fatty acid profile of transgenic yeast detected by gas chromatography-mass spectrometry illustrated that the enzyme MiD6FAD could convert linoleic and α - linolenic acids to γ-linolenic and stearidonic acids, respectively, demonstrating that MiD6fad encoded a Δ6 FAD. A 1 965-bp fragment of the cloned 2 347-bp 5′-upstream region of MiD6fad was next subcloned and fused upstream with green fluorescent protein (GFP) gene to replace the GAL1 promoter of the vector pYES2. The generated construct was transformed into S. cerevisiae for function determination. Confocal microscopic images of the transformed line illustrated that this inserted fragment could drive GFP expression, which was further verified by fluorescence intensity quantification and Western blot analysis using anti- GFP antibody. The conversion efficiency (approximately 2% - 3%) of MiD6FAD was much lower than the reported ω 3 FAD and Δ6 elongase in this microalga, suggesting that MiD6FAD catalysed the possible ratelimiting step for ArA biosynthesis. The presence of several putative cis -acting regulatory elements in this identified promoter sheds new light on the regulation mechanism research of Δ6 FAD transcription for the ArA production in M. incisa in changing environmental factors.

Temperature and food preference

Diet On a cold day, hot soup seems nice. This desire has a fundamental evolutionary basis that may lie in survival. Brankatschk et al. provided Drosophila fly larvae with a choice of food types: one containing only yeast and another consisting only of plant material. At moderate temperatures, yeast was preferred, but at cold temperatures, the larvae's preference shifted to plant material. When these larvae metamorphosed into adult flies, they showed increased cold resistance and improved survival in the winter, possibly because the plant fatty acids enhance membrane fluidity and motor coordination. Dev. Cell. 46 , 781 (2018).

Starch Deficiency Enhances Lipid Biosynthesis and Turnover in Leaves.

Starch and lipids represent two major forms of carbon and energy storage in plants and play central roles in diverse cellular processes. However, whether and how starch and lipid metabolic pathways interact to regulate metabolism and growth are poorly understood. Here, we show that lipids can partially compensate for the lack of function of transient starch during normal growth and development in Arabidopsis (Arabidopsis thaliana). Disruption of starch synthesis resulted in a significant increase in fatty acid synthesis via posttranslational regulation of the plastidic acetyl-coenzyme A carboxylase and a concurrent increase in the synthesis and turnover of membrane lipids and triacylglycerol. Genetic analysis showed that blocking fatty acid peroxisomal β-oxidation, the sole pathway for metabolic breakdown of fatty acids in plants, significantly compromised or stunted the growth and development of mutants defective in starch synthesis under long days or short days, respectively. We also found that the combined disruption of starch synthesis and fatty acid turnover resulted in increased accumulation of membrane lipids, triacylglycerol, and soluble sugars and altered fatty acid flux between the two lipid biosynthetic pathways compartmentalized in either the chloroplast or the endoplasmic reticulum. Collectively, our findings provide insight into the role of fatty acid β-oxidation and the regulatory network controlling fatty acid synthesis, and they reveal the mechanistic basis by which starch and lipid metabolic pathways interact and undergo cross talk to modulate carbon allocation, energy homeostasis, and plant growth.

Mechanisms Underlying Establishment of Arbuscular Mycorrhizal Symbioses.

Most land plants engage in mutually beneficial interactions with arbuscular mycorrhizal (AM) fungi, the fungus providing phosphate and nitrogen in exchange for fixed carbon. During presymbiosis, both organisms communicate via oligosaccharides and butenolides. The requirement for a rice chitin receptor in symbiosis-induced lateral root development suggests that cell division programs operate in inner root tissues during both AM and nodule symbioses. Furthermore, the identification of transcription factors underpinning arbuscule development and degeneration reemphasized the plant's regulatory dominance in AM symbiosis. Finally, the finding that AM fungi, as lipid auxotrophs, depend on plant fatty acids (FAs) to complete their asexual life cycle revealed the basis for fungal biotrophy. Intriguingly, lipid metabolism is also central for asexual reproduction and interaction of the fungal sister clade, the Mucoromycotina, with endobacteria, indicative of an evolutionarily ancient role for lipids in fungal mutualism.