Characterization of light-dependent regulation of state transitions in gymnosperms

Abstract

The goal of this study was to characterize the light-dependent regulation of state transitions in gymnosperms. Two species of conifer were examined: eastern white pine (Pinus strobus L.) and white spruce [Picea glauca (Moench) Voss], as well as the angiosperm pumpkin (Cucurbita pepo L. subsp. pepo). Both diurnal time courses in the field and manipulated light experiments in growth chambers were conducted. Results from chlorophyll fluorescence analysis indicated that pumpkin was able to use a larger fraction of absorbed light to drive photochemistry and retain a lower reduction state at a given light intensity relative to the conifers. Results from western blots using anti-phosphothreonine demonstrate that in field conditions, conifers maintained higher light-harvesting complex II (LHCII) phosphorylation than pumpkin; however, this was likely due to a more variable light environment. Manipulated light experiments showed that general patterns of light-dependent LHCII phosphorylation were similar in conifers and pumpkin, with low levels of LHCII phosphorylation occurring in darkness and maximal levels occurring in low light conditions. However, high light-dependent dephosphorylation of LHCIII appears to be regulated differently in conifers, with conifers maintaining phosphorylation of LHCII proteins at higher excitation pressure compared with pumpkin. Additionally, spruce needles maintained relatively high phosphorylation of LHCII even in very high light conditions. Our results suggest that this difference in dephosphorylation of LHCII may be due to differences in the stromal redox status in spruce relative to pine and pumpkin.

Specific thylakoid protein phosphorylations are prerequisites for overwintering of Norway spruce ( Picea abies ) photosynthesis

“…6 ). The destacking and linearization of thylakoids upon formation of 3p-LHCII could, in turn, lead to loosening of the lateral heterogeneity of photosystems and thereby increase the chance for PSII–PSI spillover, which has been suggested to be involved in sustained NPQ ( 1 , 17 , 46 ). Conversely, a coherent restoration of Fv/Fm and dephosphorylation of 3p-LHCII occurred upon recovery of spruce needles from sustained NPQ ( Fig.…”

Functions and Evolution of Lhcb Isoforms Composing LHCII, the Major Light Harvesting Complex of Photosystem II of Green Eukaryotic Organisms

“…Once again, the Pinus and Picea species, both lacking Lhcb3 and CP24, might be interesting models to study the effect of these proteins on state transitions in plants. To our knowledge, this regulation mechanism has been little studied in gymnosperms so far, although recent studies found a relatively high phosphorylation of LHCII in high light in conifers compared to angiosperms [107,108], suggesting a different regulation of energy dissipation and possibly also of state transitions. It is nonetheless possible that the absence of Lhcb3 in pine species facilitates this higher phosphorylation.…”