Genetic Manipulation of Isoprene Emissions in Poplar Plants Remodels the Chloroplast Proteome

Abstract

Biogenic isoprene (2-methyl-1,3-butadiene) improves the integrity and functionality of thylakoid membranes and scavenges reactive oxygen species (ROS) in plant tissue under stress conditions. On the basis of available physiological studies, we hypothesized that the suppression of isoprene production in the poplar plant by genetic engineering would cause changes in the chloroplast protein pattern, which in turn would compensate for changes in chloroplast functionality and overall plant performance under abiotic stress. To test this hypothesis, we used a stable isotope-coded protein-labeling technique in conjunction with polyacrylamide gel electrophoresis and liquid chromatography tandem mass spectrometry. We analyzed quantitative and qualitative changes in the chloroplast proteome of isoprene-emitting and non isoprene-emitting poplars. Here we demonstrate that suppression of isoprene synthase by RNA interference resulted in decreased levels of chloroplast proteins involved in photosynthesis and increased levels of histones, ribosomal proteins, and proteins related to metabolism. Overall, our results show that the absence of isoprene triggers a rearrangement of the chloroplast protein profile to minimize the negative stress effects resulting from the absence of isoprene. The present data strongly support the idea that isoprene improves/stabilizes thylakoid membrane structure and interferes with the production of ROS.

Knocking Down of Isoprene Emission Modifies the Lipid Matrix of Thylakoid Membranes and Influences the Chloroplast Ultrastructure in Poplar

“…To further understand how the structural changes were related to the protein enrichment in photosynthetic membranes, we extracted mass spectrometry (MS) data from our recent proteome study (Velikova et al, 2014). The concentrations of PSI-PSI reaction centers (RCI) and PSII-PSII reaction centers (RCII) were strongly decreased in NE chloroplasts compared with IE chloroplasts (Fig.…”

“…We examined the involvement of lipid content and fatty acid composition in NE and IE chloroplasts, compared with chlorophyll fluorescence measurements, MDA contents, and previously described proteomic differences (Velikova et al, 2014). Principal component analysis (PCA) showed that the isoprene emission traits reflected the largest variance of the measured data, indicated by the separation between NE and IE samples in the first two principal components (Supplemental Fig.…”

“…Indeed, we could demonstrate that the proteins related to photosynthesis were strongly down-regulated in NE compared with IE plants (Figs. 7 and 8;Velikova et al, 2014).…”

“…It was also shown that isoprene improves the stability of PSII light-harvesting complex II (LHCII) through the modification of pigment-protein complex organization in thylakoid membranes (Velikova et al, 2011). Moreover, we recently showed that knocking down isoprene emission in poplar remodels the chloroplast proteome (Velikova et al, 2014). The lack of isoprene resulted in the down-regulation of proteins associated with the light reactions of photosynthesis, redox regulation, and oxidative stress defenses and several proteins responsible for lipid metabolism (Velikova et al, 2014).…”

“…Moreover, we recently showed that knocking down isoprene emission in poplar remodels the chloroplast proteome (Velikova et al, 2014). The lack of isoprene resulted in the down-regulation of proteins associated with the light reactions of photosynthesis, redox regulation, and oxidative stress defenses and several proteins responsible for lipid metabolism (Velikova et al, 2014).…”