Functional genomics of Populus leaves

Abstract

Understanding the ecophysiological aspects of plant adaption require better knowledge of the regulation of gene expression by environmental factors. Especially environmental adaption of perennial plants, that have adopted a more long-term ecological strategy than annual plants, remains to be elucidated. We are interested in the global changes in genes expression in Populus leaves and have, as a part of the Populus EST program, produced 4842 ESTs from young non-stressed leaves and around 5500 ESTs from senescing leaves. The gene expression pattern in young and senescing leaves was strikingly different: 38% of the clones from young leaves encoded for photosynthetic proteins which are very poorly represented among the senescence ESTs. In contrast, for example metallothionein, proteases, early light-inducible proteins (ELIP), mitochondrial formated dehydrogenase and many senescence-associated genes were abundant among the senescence ESTs. We have also indirectly estimated amount of chloroplast protein synthesis. One of our aims is to bring functional genomics out in the field, and monitor the alteration of the transcriptional profile in leaves and identify the regulons in poplar leaves using DNA microarrays. We have created the "Populus-chip" containing over 13.000 annotated cDNA clones selected from over 35.000 Populus ESTs. We have collected leaves of field-grown Populus twice a week through the whole vegetation season (from bud burst to leaf abscission), analysed the samples with the Populus-chip and will present data on the global pattern of gene regulation in leaves over the growing season. We also present data on the diurnal rhythm of gene expression in Populus leaves