Genetic structure and regulation of isoprene synthase in Poplar (Populus spp.)
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Isoprene is a volatile 5-carbon hydrocarbon derived from the chloroplastic methylerythritol 2-C-methyl-d-erythritol 4-phosphate isoprenoid pathway. In plants, isoprene emission is controlled by the enzyme isoprene synthase; however, there is still relatively little known about the genetics and regulation of this enzyme. Isoprene synthase gene structure was analysed in three poplar species. It was found that genes encoding stromal isoprene synthase exist as a small gene family, the members of which encode virtually identical proteins and are differentially regulated. Accumulation of isoprene synthase protein is developmentally regulated, but does not differ between sun and shade leaves and does not increase when heat stress is applied. Our data suggest that, in mature leaves, isoprene emission rates are primarily determined by substrate (dimethylallyl diphosphate, DMADP) availability. In immature leaves, where isoprene synthase levels are variable, emission levels are also influenced by the amount of isoprene synthase protein. No thylakoid isoforms could be identified in Populus alba or in Salix babylonica. Together, these data show that control of isoprene emission at the genetic level is far more complicated than previously assumed.
KeywordsIsoprene Poplar Isoprene synthase Developmental regulation Isoprenoid pathway
This research was funded by the UK Biotechnology and Biological Sciences Research Council (BBSRC) grant number BBS/B/12172. The full-length anti-isoprene synthase antibody was kindly provided by Dr Jörg-Peter Schnitzler, IMK-IFU, Garmisch, Germany. We thank Dr Oksana Zakhleniuk and Mr Daniel Exton for skilled technical assistance.
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