Identification of Cuticular and Web Lipids of the Spider Argiope bruennichi

Emerging evidence shows that the cuticular and silk lipids of spiders are structurally more diverse than those of insects, although only a relatively low number of species have been investigated so far. As in insects, such lipids might play a role as signals in various contexts. The wasp spider Argiope bruennichi has probably the best investigated chemical communication system within spiders, including the known structure of the female sex pheromone. Recently we showed that kin-recognition in A. bruennichi could be mediated through the cuticular compounds consisting of hydrocarbons and, to a much larger proportion, of wax esters. By use of mass spectrometry and various derivatization methods, these were identified as esters of 2,4-dimethylalkanoic acids and 1-alkanols of varying chain lengths, such as tetradecyl 2,4-dimethylheptadecanoate. A representative enantioselective synthesis of this compound was performed which proved the identifications and allowed us to postulate that the natural enantiomer likely has the (2R,4R)-configuration. Chemical profiles of the silk and cuticular lipids of females were similar, while male cuticular profiles differed from those of females. Major components of the male cuticular lipids were tridecyl 2,4-dimethyl-C17-19 alkanoates, whereas those of females were slightly longer, comprising tridecyl 2,4-dimethyl-C19-21 alkanoates. In addition, minor female-specific 4-methylalkyl esters were detected.

Cuticular Wax Composition is Essential for Plant Recovery Following Drought with Little Effect under Optimal Conditions

Despite decades of extensive study, the role of cuticular lipids in sustaining plant fitness is far from being understood. To answer this fundamental question, we employed genome editing in tree tobacco (Nicotiana glauca) plants and generated mutations in 16 different cuticular lipids-related genes. We chose tree tobacco due to the abundant, yet simply composed epicuticular waxes deposited on its surface. Five out of 9 different mutants that displayed a cuticular lipids-related phenotype were selected for in depth analysis. They had either reduced total wax load or complete deficiency in certain wax components. This led to substantial modification in surface wax crystal structure and to elevated cuticular water loss. Remarkably, under non-stressed conditions, mutant plants with altered wax composition did not display elevated transpiration or reduced growth. However, once exposed to drought, plants lacking alkanes were not able to strongly reduce their transpiration, leading to leaf death and impaired recovery upon resuscitation, and even to stem cracking, a phenomenon typically found in trees experiencing drought stress. In contrast, plants deficient in fatty alcohols exhibited an opposite response, having reduced cuticular water loss and rapid recovery following drought. This deferential response was part of a larger trend, of no common phenotype connecting plants with a glossy appearance. We conclude that alkanes are essential under drought response and much less under normal non-stressed conditions, enabling plants to seal their cuticle upon stomatal closure, reducing leaf death and facilitating a speedy recovery.

Similar Is Not the Same – Mate Recognition in a Parasitoid Wasp

Finding and recognizing a suitable mate is a key prerequisite to reproductive success. Insects often recognize prospective mates using chemical cues and signals. Among these, cuticular lipids commonly serve for mate recognition at close range. The lipid layer on the surface of insects is comprised predominantly of cuticular hydrocarbons (CHCs), though more polar compounds may also be present. While the composition of the cuticular profile is typically species specific, many species additionally show differentiation between the sexes by sex specific compounds and/or compound ratios. It is often assumed that a clear sexual dimorphism of cuticular lipid profiles is a prerequisite for a potential function as sex pheromones. Both, sex specific single compounds or the profiles as a whole have been shown to serve as sex pheromones in parasitoid wasps. Here, we studied parasitoid wasps of the species Tachinaephagus zealandicus (Encyrtidae, Hymenoptera). Chemical analyses revealed that this species presents a case where males and females produce the same set of CHCs in similar relative amounts. To test whether these wasps nonetheless can use the cuticular lipids for close range mate recognition, we tested the reaction of males toward freeze-killed conspecifics. Males showed copulation behavior exclusively toward dead females, but not toward dead males. Dead females from which the cuticular lipids had been removed did not elicit copulation behavior by tested males. Reapplication of female whole body extracts restored bioactivity, and males reacted with copulation attempts as often as toward the freeze-killed females. Bioassays with lipid fractions revealed that only the CHC fraction was bioactive on its own. Here, again, males reacted to female, but not to male CHCs. Our results indicate that these wasps are capable of using CHCs for close range sex recognition despite the similarity of male and female profiles.

Metamorphosis-related changes in the free fatty acid profiles of Sarcophaga (Liopygia) argyrostoma (Robineau-Desvoidy, 1830)

The flies of the Sarcophagidae, widespread throughout the temperate zone, are of great significance in Medicine, Veterinary science, Forensics and Entomotoxicology. Lipids are important elements of cell and organelle membranes and a source of energy for embryogenesis, metamorphosis and flight. Cuticular lipids protect from desiccation and act as recognition cues for species, nest mates and castes, and are a source of various pheromones. The free fatty acid (FFA) profile of cuticular and internal extracts of Sarcophaga (Liopygia) argyrostoma (Robineau-Desvoidy, 1830) larvae, pupae and adults was determined by gas chromatography–mass spectrometry (GC–MS). The larvae, pupae and adults contained FFAs from C5:0 to C28:0. The extracts differed quantitatively and qualitatively from each other: C18:1 > C16:1 > C16:0 > C18:0 predominated in the cuticular and internal extracts from the larvae and adults, while 18:1 > C16:0 > C16:1 > C18:0 predominated in the pupae. The FFA profile of the cuticle varies considerably between each development stage: C23:0 and C25:0 are only present in larvae, C28:0 in the pupal cuticle, and C12:1 and C18:3 in internal extracts from adults. The mechanisms underlying this diversity are discussed herein.

Evaluation of the functional role of the maize Glossy2 and Glossy2-like genes in cuticular lipid deposition

ABSTRACTPlant epidermal cells express unique molecular machinery that juxtapose the assembly of intracellular lipid components and the unique extracellular cuticular lipids that are unidirectionally secreted to plant surfaces. In maize (Zea mays L.), mutations at the glossy2 (gl2) locus affect the deposition of extracellular cuticular lipids. Sequence-based genome scanning identified a novel gl2 homolog in the maize genome, Gl2-like. Sequence homology identifies that both the Gl2-like and Gl2 genes are members of the BAHD superfamily of acyltransferases, with close sequence homology to the Arabidopsis CER2 gene. Transgenic experiments demonstrate that Gl2-like and Gl2 functionally complement the Arabidopsis cer2 mutation, with differential impacts on the cuticular lipids and the lipidome of the plant, particularly affecting the longer alkyl chain acyl lipids, particularly at the 32-carbon chain length. Site-directed mutagenesis of the putative BAHD catalytic HXXXDX-motif indicates that Gl2-like requires this catalytic capability to fully complement the cer2 function, but Gl2 can accomplish this without the need for this catalytic motif. These findings demonstrate that both Gl2 and Gl2-like overlap in their cuticular lipid function, however the two genes have evolutionary diverged to acquire non-overlapping functions.One-sentence summaryTransgenesis dissection of the functional roles of the maize Glossy2 and Glossy2-Like genes in cuticular lipid deposition.