High-throughput analysis of transcriptome variation during water deficit in a poplar hybrid: a general overview

Poplar interspecific hybrids are one of the most important forest crops. In order to obtain data on molecular responses of forest trees to drought, Illumina sequencing technology was used to determine the sequence of most gene transcripts. This approach identified genes that contribute to tolerance to water-limiting environments, contributing to the long-term aim of developing strategies to improve plant productivity under drought. We generated 72,197,113 sequence reads, each 51 nt in length, encompassing 3.68 Gb of sequence from 12 cDNA libraries obtained from leaves of plants of a hybrid between Populus deltoides and Populus nigra subjected or not to moderate or severe drought. The expression of 41,335 poplar genes included in the Populus trichocarpa Phytozome database was studied by mapping Illumina cDNA reads on poplar unigene models. Expressed genes were characterised by gene ontology and by determining the metabolic pathway to which they belong.Most genes detected were expressed in control and drought-treated plants; however, a number of genes thatwere observedwere significantly induced or repressed by drought. Induction or repression of most genes was more common after severe (relative water content around 55–60%) than aftermoderate water deficit (around 85 %) even for genes that usually respond promptly to changes in environmental conditions, such as those encoding transcription factors. The dataset of expression profiles will be useful for future studies on responses to other stimula and for crop improvement of poplar.