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

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.