Abstract
Salix integra is a shrub willow native to northeastern China, Japan, Korea, and Primorsky Krai in the far southeast of Russia, and has been identified as cadmium (Cd)-accumulating trees in recent years. Although many physiological studies have been conducted with these plants, little is known about the molecular basis underlying Cd response in this plant, and this is confirmed by the very few number of gene sequences (only 39 nucleotide sequences) available in public databases. Advances in genomics for Salix are promising for future improvement in identification of new candidate genes involved in metal tolerance and accumulation. Thus, high-throughput transcriptome sequencing is essential for generating enormous transcript sequences from S. integra, especially for the purpose of Cd toxicity-responsive genes discovery. Using Illumina paired-end sequencing, approximately 60.05 million high-quality reads were obtained. De novo assembly yielded 80,105 unigenes with an average length of 703 bp, A total of 50,221 (63%) unigenes were further functionally annotated by comparing their sequences to different proteins and functional domain databases. GO annotation reveals 1849 Cd responsive genes involving in Cd binding, transport, and detoxification and cellular Cd homeostasis, and these genes were highly enriched in plant response to Cd ion and Cd ion transport. By searching against the PlantCyc database, 509 unigenes were assigned to 14 PlantCyc pathways related to Cd transport and cellular detoxification, and many of them are genes encoding heavy metal ATPases (HMAs), nature resistance-associated with microphage proteins (NRAMPs), ATP-binding cassette (ABC) transporters, etc., Comprehensive RT-qPCR analysis of these selected genes in different tissues of S. integra under the control and Cd treatment revealed metallothionein-like protein (MT2A and MT2B), Metal tolerance protein (MTP1), ABCB25, NRAMP5, and ZIP1 may be involved in the Cd transport and detoxification in leaves, while NRAMP2, ZIP8, and NRAMP5 may be related to Cd transport in roots. Our study will enrich the sequence information of S. integra in public database, and would provide some new understanding of the molecular mechanisms of heavy metal tolerance and detoxification in willows.
Highlights
Cadmium (Cd) is known to be one of the most toxic non-essential elements in soil
Most of genes involving in heavy metals (HMs) uptake, transport, sequestration, and detoxification in woody plants were restricted to Populus (Marmiroli et al, 2011; Luo et al, 2016)
Willow and poplar are closely related species, they are similar in many respects, for example, both species are propagated as clones, and could accumulate moderate contents of HMs in their aerial parts
Summary
Cadmium (Cd) is known to be one of the most toxic non-essential elements in soil. It is very mobile and accumulates in plant tissues, and readily enters into food chain, which cause potential threat to human health with the high risk of causing cancer (Nawrot et al, 2006; Satarug et al, 2010). Some of the cultivated varieties, such as Yizhibi and Weishanhu, displayed excellent in biomass production and environmental adaptation They could accumulate up to 288 mg Cd kg−1 dry weight in their leaves, and more interestingly, S. integra was shown to be able to grow in solutions with 90 μmol/L of Cd concentration with moderate symptoms of toxicity (Wang et al, 2013). This means S. integra could accumulate desired Cd in the aboveground tissues, and have high tolerance to Cd in their roots. The metal-accumulating ability of S. integra has been well documented, basic understanding of molecular mechanisms of metal tolerance, and accumulation is very limited
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
