Genome-Wide Analysis of Gene Expression in Response to Drought Stress in Populus simonii

Abstract

Drought tolerance varies considerably in different species of Populus, and is a complex trait, involving the interplay of a vast array of genes. Although Populus simonii is one of the most important commercial plantation tree species in China, genes controlling drought-stress tolerance in this organism have not yet been identified. Here, tran- scriptomic changes during drought stress in P. simonii were detected using an Affymetrix GeneChip. In total, 1,028 transcripts were identified as differentially expressed under drought stress, of which 496 transcripts increased and 532 decreased in abundance (two-way ANOVA, fold change >4 and P<0.01). Expression changes of 20 candidate genes were validated by real-time PCR, indicating significant dif- ferences between the controls and water-deficit treatments. Gene annotation demonstrated that the majority of these P. simonii genes encode products involved in phytohormone metabolism, osmoregulation, and oxidative stress. Based on gene ontology (GO) classification, the increased genes were classified into six significantly enriched GO terms involved in 64 pathways, and the decreased genes were classified into 39 significantly enriched GO terms representing 42 path- ways. Bioinformatics analysis showed that the differential expression of plant hormone-related, transcription factor, cytochrome P450 gene superfamily, carbohydrate metabo- lism, and amino acid transporter genes may contribute to drought-stress tolerance in P. simonii. Our study provides global gene expression patterns during drought stress and will be valuable for further study of the molecular mecha- nisms of drought tolerance in P. simonii.