RNA-Seq reveals genotype-specific molecular responses to water deficit in eucalyptus
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2011
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Background: In a context of climate change, phenotypic plasticity provides long-lived species, such as trees, with
the means to adapt to environmental variations occurring within a single generation. In eucalyptus plantations,
water availability is a key factor limiting productivity. However, the molecular mechanisms underlying the
adaptation of eucalyptus to water shortage remain unclear. In this study, we compared the molecular responses of
two commercial eucalyptus hybrids during the dry season. Both hybrids differ in productivity when grown under
water deficit.
Results: Pyrosequencing of RNA extracted from shoot apices provided extensive transcriptome coverage - a
catalog of 129,993 unigenes (49,748 contigs and 80,245 singletons) was generated from 398 million base pairs, or
1.14 million reads. The pyrosequencing data enriched considerably existing Eucalyptus EST collections, adding
36,985 unigenes not previously represented. Digital analysis of read abundance in 14,460 contigs identified 1,280
that were differentially expressed between the two genotypes, 155 contigs showing differential expression
between treatments (irrigated vs. non irrigated conditions during the dry season), and 274 contigs with significant
genotype-by-treatment interaction. The more productive genotype displayed a larger set of genes responding to
water stress. Moreover, stress signal transduction seemed to involve different pathways in the two genotypes,
suggesting that water shortage induces distinct cellular stress cascades. Similarly, the response of functional
proteins also varied widely between genotypes: the most productive genotype decreased expression of genes
related to photosystem, transport and secondary metabolism, whereas genes related to primary metabolism and
cell organisation were over-expressed.
Conclusions: For the most productive genotype, the ability to express a broader set of genes in response to water
availability appears to be a key characteristic in the maintenance of biomass growth during the dry season. Its
strategy may involve a decrease of photosynthetic activity during the dry season associated with resources
reallocation through major changes in the expression of primary metabolism associated genes. Further efforts will
be needed to assess the adaptive nature of the genes highlighted in this study.
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VILLAR, Emilie; KLOPP, Christophe; NOIROT, Céline; NOVAES, Evandro; KIRST, Matias; PLOMION, Christophe; GION, Jean-Marc. RNA-Seq reveals genotype-specific molecular responses to water deficit in eucalyptus. BMC Genomics, New York, v. 12, p. 538, 2011.