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Functional Genomics on Wood Formation in Eucalyptus

Final Activity Report Summary - WOODGENEUS (Functional Genomics on Wood Formation in Eucalyptus)

Eucalyptus species, renowned for their fast growth, optimal wood properties and wide adaptability are amongst the most planted hardwoods in the world. Indeed, Eucalyptus plantations represent a major economic activity in the EU, as a major source of raw material for the European pulp and paper industry, among many other wood-derived products. The increasing demand for wood might be answered by improving wood quality and productivity through tree domestication. Because Eucalyptus species are still at the early stages of domestication, there is a huge potential in developing marker-assisted selection programs. With this aim, we decided as a first step to undertake a large sequencing project to get a comprehensive picture of the genes involved in wood formation.

The sequencing of a normalised developing-xylem cDNA library as well as of subtractive libraries (juvenile wood versus mature and vice versa) led to 9 712 high quality wood-related Eucalyptus ESTs sequences, thus significantly increasing the representation of Eucalyptus transcripts in public databases. Subsequent assembly and annotation of these sequences produced a set of 3 928 unigenes (2 479 contigs and 1 449 singletons) named 'EUCAWOOD'. The annotation of the EUCAWOOD set revealed key functional categories involved in xylogenesis, more particularly genes families involved in biosynthesis and assembly of cell walls. The EUCAWOOD dataset was also mined for SSRs using, yielding a total of 641 putative microsatellites. Finally, a publicly accessible web interface, which supports multiple queries on the wood-related unigenes and their functional annotation, has been developed to mine this new Eucalyptus genomic resource.

This set of publicly available annotated sequences is instrumental for candidate gene approaches, custom array development and molecular breeding programs aimed at improving and modulating wood properties. Indeed, we used 3 000 clones from different subtractive libraries to build a custom microarray. Hybridisations were performed using contrasted wood samples highlighting a number of genes differentially expressed which are being mapped on Eucalyptus genetic linkages maps by partners such as CIRAD and RAIZ.

In conclusion, this work produced a large set of wood-related Eucalyptus unigenes (EUCAWOOD), which is a valuable resource for functional genomics studies of wood formation and molecular breeding programs in this economically important genus. Moreover, these genes might help customise wood properties for different end-uses.