Abstract
Ammopiptanthus mongolicus (Maxim. Ex Kom.) Cheng f., a relic tree of the Tertiary period, plays a critical role in maintaining desert ecosystems in the Mid-Asia region. Genome-scale gene expression profiling studies will provide deep insight into the molecular mechanism underlying the drought tolerance of A. mongolicus. In the present study, we investigated the transcriptional changes induced by drought treatment in A. mongolicus leaves by establishing a comprehensive transcriptome database and then performing a Digital Gene Expression (DGE) analysis using Solexa sequencing technology. A comprehensive transcriptome database was obtained by assembling the Illumina unigenes with expressed sequence tags (EST) available publicly, and other high throughput sequencing data. To analyze the dynamic and complicated gene regulation network during PEG6000-induced drought treatment in leaves of A. mongolicus, a time-course gene expression analysis was performed using tag-based DGE technology, which identified 437, 1,247 and 802 differentially expressed transcripts in 1, 24 and 72 h drought stress libraries, respectively. GO and KEGG analyses revealed hormone signal transduction and phenylpropanoid biosynthesis were enriched during drought treatment. A batch of drought-regulated transcription factor transcripts were identified, including the subsets of HD-ZIP, bZIP, WRKY, AP2/ERF and bHLH family members, which may play roles in drought response in A. mongolicus. The sequence collection assembled in the present study represents one of the most comprehensive transcriptome databases for A. mongolicus currently. The differentially expressed transcripts identified in our study provide a good start for identifying the key genes in stress response and performing functional analysis to reveal their roles in stress adaptation in planta.
Highlights
Forest ecosystems have been transformed, to a large extent, by global climate change
All read data were deposited in the National Center for Biotechnology Information (NCBI) and can be accessed in the Short Read Archive (SRA) under the accession number SRX381742
The results suggest that, besides the hormone signal transduction and secondary metabolites biosynthesis, amino acid metabolism, lipid metabolism, sugar metabolism, endocytosis, and plant-pathogen interaction were involved in the drought response in A. mongolicus leaves
Summary
Forest ecosystems have been transformed, to a large extent, by global climate change. As the climate became colder and drier in late Holocene, which was partly caused by change in the intensity of the Asian summer monsoon, the forest was gradually replaced by temperate steppe and by desert [1,2]. Almost all evergreen broadleaf trees in mid-Asia have vanished. Two evergreen broadleaf plant species, Ammopiptanthus mongolicus Pop.) Cheng f., the only two species in genus Ammopiptanthus (Leguminosae), survive the dramatic climate change. Ammopiptanthus is believed to play an essential role in maintaining desert ecosystems in the Mid-Asia region [3]. Genome level studies on plants in genus Ammopiptanthus will promote our understanding on how the plant responds to climate change
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