Project description:The ability of plants to acquire and use water is critical in determining life-history traits such as growth, flowering, and allocation of biomass into reproduction. In this context, a combination of functionally linked traits is essential for plants to respond to environmental changes in a coordinated fashion to maximize resource use efficiency. We analyzed different water-use traits in Arabidopsis ecotypes to identify functionally linked traits that determine water use and plant growth performance. Water-use traits measured were (i) leaf-level water-use efficiency (WUE i ) to evaluate the amount of CO 2 fixed relative to water loss per leaf area and (ii) short-term plant water use at the vegetative stage (VWU) as a measure of whole-plant transpiration. Previously observed phenotypic variance in VWU, WUE i and life-history parameters, highlighted C24 as a valuable ecotype that combined drought tolerance, preferential reproductive biomass allocation, high WUE i , and reduced water use. We therefore screened 35 Arabidopsis ecotypes for these parameters, in order to assess whether the phenotypic combinations observed in C24 existed more widely within Arabidopsis ecotypes. All parameters were measured on a short dehydration cycle. A segmented regression analysis was carried out to evaluate the plasticity of the drought response and identified the breakpoint as a reliable measure of drought sensitivity. VWU was largely dependent on rosette area, but importantly the drought sensitivity and plasticity measures were independent of the transpiring leaf surface. A breakpoint at high rSWC indicated a more drought-sensitive plant that closed stomata early during the dehydration cycle and consequently showed stronger plasticity in leaf-level WUE i parameters. None of the sensitivity, plasticity, or water-use measurements were able to predict the overall growth performance; however, there was a general trade-off between vegetative and reproductive biomass. PCA and hierarchical clustering revealed that C24 was unique among the 35 ecotypes in uniting all the beneficial water use and stress tolerance traits, while also maintaining above average plant growth. We propose that a short dehydration cycle, measuring drought sensitivity and VWU is a fast and reliable screen for plant water use and drought response strategies.

Project description:Across evolutionary time, nearly all animal species have harnessed photoperiod to initiate processes that ultimately influence seasonal behavior and life history traits. In the freshwater cladoceran Daphnia magna, the effect of photoperiod on various life history traits has generally been investigated in conjunction with additional environmental stimuli. In the present study, we sought to untangling responses directly attributable to photoperiod in D. magna and identify the molecular processes underlying resultant behavioral and life history responses using functional analysis of global transcriptomic expression. D. magna were exposed to five different photoperiods immediately post-hatch for 21d where a standard long-day photoperiod of 16 hours light and 8 hours dark (16L:8D) served as the control relative to 4L:20D, 8L:16D, 12L:12L, and 20L:4D photoperiods. Entrainment to short-day photo-periods (4L:20D, 8L:16D, and 12L:12L) resulted in significantly increased light-avoidance behaviors relative to the control photoperiod where young Daphnia (7d old) displayed the most pronounced avoidance responses. Correspondingly, functional transcriptomics identified differential transcriptional expression of genes involved in glutamate signaling, which is critical in arthropod light-avoidance responses, as well as period circadian protein and proteins coding F-box/LRR-repeat domains, all of which contribute to establishing circadian rhythms in arthropods. Short-day photoperiods also induced increased metabolic rates which corresponded with broad-scale changes in transcriptional expression across multiple systems-level energy metabolism pathways. The most striking observation was increased male production across short-day photoperiods (4L:20D, 8L:16D, and 12L:12D). Transcriptional expression consistent with multiple putative mechanisms of male production were observed including expression suggestive of increased glutamate signaling; a response observed to induce male production in D. pulex via photo-period sensitive mechanisms. Overall, the results demonstrate the importance of photoperiod on behavior and life history trajectories in D. magna where we have now established multiple putative mechanistic pathways underlying several critical responses.

Dataset Information

Variation in life-history traits among Daphnia and its relationship to species-level responses to phosphorus limitation.

Publications

Variation in life-history traits among <i>Daphnia</i> and its relationship to species-level responses to phosphorus limitation.

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