New publication – Spectacular oscillations in plant isoprene emission explain the enigmatic CO2 response

Text by Lauri Laanisto

Well, I do love a paper which says both spectacular and enigmatic in its title! That should be quite a hook for news agencies? Ok. As the one sentence summary says: Oscillations in isoprene emission demonstrate that the emission is controlled by chloroplast reductant status. There! I think this summarizes this paper quite nicley, without the spectacularity of pertinent enigma(s). (I´m not particularly competent in this topic, so I´ll withhold further comment…)

isopreneskeem

Figure 9 from the paper – Simple scheme of photosynthetic energy-metabolite supply for isoprene synthesis and processes inducing oscillations in photosynthesis and isoprene emission.

Citation: Rasulov, B., Talts, E., & Niinemets, U. (2016). Spectacular oscillations in plant isoprene emission explain the enigmatic CO2 response. Plant Physiology, . (link to full text)

Abstract:

Plant isoprene emissions respond to light and temperature similarly to photosynthesis, but CO2-dependencies of isoprene emission and photosynthesis are profoundly different with photosynthesis increasing and isoprene emissions decreasing with increasing CO2 concentration due to reasons not yet understood. We studied isoprene emission, net assimilation rate and chlorophyll fluorescence under different CO2 and O2 concentrations in the strong isoprene emitter hybrid aspen (Populus tremula x P. tremuloides), and used rapid changes in ambient CO2 or O2 concentrations or light level to induce oscillations. As isoprene-emitting species support a very high steady-state chloroplastic pool sizes of the primary isoprene substrate, dimethylallyl diphosphate (DMADP), that can mask the effects of oscillatory dynamics on isoprene emission, the size of DMADP pool was experimentally reduced by either partial inhibition of isoprenoid synthesis pathway by fosmidomycin-feeding or by changes in ambient gas concentrations leading to DMADP pool depletion in intact leaves. In feedback-limited conditions, oscillations in photosynthesis and isoprene emission were repeatedly induced by rapid environmental modifications in both partly fosmidomycin-inhibited leaves and in intact leaves. The oscillations in net assimilation rate and isoprene emission in feedback-inhibited leaves were in the same phase, and relative changes in the pools of photosynthetic metabolites and DMADP estimated by in vivo kinetic methods were directly proportional through all oscillations induced by different environmental perturbations. We conclude that the oscillations in isoprene emission provide direct experimental evidence demonstrating that the response of isoprene emission to changes in ambient gas concentrations is controlled by the chloroplastic reductant supply.

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