Vertical transmission of horizontally acquired social information in sticklebacks: implications for transgenerational plasticity.

There is growing evidence that offspring receive information about their environment vertically, i.e. from their parents (environmental parental effects or transgenerational plasticity). For example, parents exposed to predation risk may produce offspring with heightened antipredator defences. At the same time, organisms can gain information about the environment horizontally, from conspecifics. In this study, we provide some of the first evidence that horizontally acquired social information can be transmitted vertically across generations. Three-spined stickleback (Gasterosteus aculeatus) fathers produced larval offspring with altered antipredator behaviour when fathers received visual and olfactory cues from predator-chased neighbours. Although fathers did not personally witness their neighbours being chased (i.e. they never saw the predator), changes in offspring traits were similar to those induced by direct paternal exposure to predation risk. These findings suggest that two different non-genetic pathways (horizontal transfer of social information, vertical transfer via sperm-mediated paternal effects) can combine to affect offspring phenotypes. The implications of simultaneous horizontal and vertical transmission are widely appreciated in the context of disease and culture; our results suggest that they could be equally important for the maintenance of phenotypic variation and could have profound consequences for the rate at which information flows within and across generations.

Are Methanol-Derived Foliar Methyl Acetate Emissions a Tracer of Acetate-Mediated Drought Survival in Plants?

Upregulation of acetate fermentation in plants has recently been described as an evolutionarily conserved drought survival strategy, with the amount of acetate produced directly correlating to survival. However, destructive measurements are required to evaluate acetate-linked drought responses, limiting the temporal and spatial scales that can be studied. Here, 13C-labeling studies with poplar (Populus trichocarpa) branches confirmed that methyl acetate is produced in plants from the acetate-linked acetylation of methanol. Methyl acetate emissions from detached leaves were strongly stimulated during desiccation, with total emissions decreasing with the leaf developmental stage. In addition, diurnal methyl acetate emissions from whole physiologically active poplar branches increased as a function of temperature, and light-dark transitions resulted in significant emission bursts lasting several hours. During experimental drought treatments of potted poplar saplings, light-dark methyl acetate emission bursts were eliminated while strong enhancements in methyl acetate emissions lasting > 6 days were observed with their initiation coinciding with the suppression of transpiration and photosynthesis. The results suggest that methyl acetate emissions represent a novel non-invasive tracer of acetate-mediated temperature and drought survival response in plants. The findings may have important implications for the future understanding of acetate-mediated drought responses to transcription, cellular metabolism, and hormone signaling, as well as its associated changes in carbon cycling and water use from individual plants to whole ecosystems.

Cell wall O-acetyl and methyl esterification patterns of leaves reflected in atmospheric emission signatures of acetic acid and methanol.

Plants emit high rates of methanol (meOH), generally assumed to derive from pectin demethylation, and this increases during abiotic stress. In contrast, less is known about the emission and source of acetic acid (AA). In this study, Populus trichocarpa (California poplar) leaves in different developmental stages were desiccated and quantified for total meOH and AA emissions together with bulk cell wall acetylation and methylation content. While young leaves showed high emissions of meOH (140 µmol m-2) and AA (42 µmol m-2), emissions were reduced in mature (meOH: 69%, AA: 60%) and old (meOH: 83%, AA: 76%) leaves. In contrast, the ratio of AA/meOH emissions increased with leaf development (young: 35%, mature: 43%, old: 82%), mimicking the pattern of O-acetyl/methyl ester ratios of leaf bulk cell walls (young: 35%, mature: 38%, old: 51%), which is driven by an increase in O-acetyl and decrease in methyl ester content with age. The results are consistent with meOH and AA emission sources from cell wall de-esterification, with young expanding tissues producing highly methylated pectin that is progressively demethyl-esterified. We highlight the quantification of AA/meOH emission ratios as a potential tool for rapid phenotype screening of structural carbohydrate esterification patterns.