Project description:Coping of evergreen conifers of boreal forests with freezing temperatures on bright winter days puts the photosynthetic machinery in great risk of oxidative damage. To survive harsh winter conditions, conifers have evolved a unique but poorly characterised photoprotection mechanism, a sustained form of non-photochemical quenching (sustained NPQ). Here we focused on functional properties and underlying molecular mechanisms related to the development of sustained NPQ in Norway spruce (Picea abies). Data was collected during four consecutive years (2016-19) from trees growing in sun and shade habitats. When day temperatures dropped below -4°C, specific N-terminally triply phosphorylated LHCB1 isoform (3p-LHCII) and phosphorylated PSBS (p-PSBS) were detected in the thylakoid membrane. Development of sustained NPQ coincided with the highest level of 3p-LHCII and p-PSBS, occurring after prolonged combination of bright winter days and temperature close to -10°C. Artificial induction of both the sustained NPQ and recovery from naturally induced sustained NPQ provided information on differential dynamics and light-dependence of 3p-LHCII and p-PSBS accumulation and dephosphorylation as essential prerequisites of sustained NPQ. Data obtained collectively suggest three novel components related to sustained NPQ in spruce. (i) Freezing temperatures induce 3p-LHCII accumulation independently of light, which is suggested to initiate de-stacking of appressed thylakoid membranes due to increased electrostatic repulsion of adjacent membranes. (ii) p-PSBS accumulation is both light- and temperature-dependent and closely linked to the initiation of sustained NPQ, which (iii) in concert with PSII photoinhibition is likely to trigger sustained NPQ in spruce.
Project description:Analysis of the subunits composition of the thylakoids protein complexes in Picea abies (Norway spruce) by means of two-dimensional large-pore Blue-Native/sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2D lpBN/SDS-PAGE) and in-gel tryptic digestion of single spots.
