• Open Access

Discovery of polymorphisms in starch-related genes in rice germplasm by amplification of pooled DNA and deeply parallel sequencing

Authors

  • Ardashir Kharabian-Masouleh,

    Corresponding author
    1. Southern Cross Plant Science, Centre for Plant Conservation Genetics, Southern Cross University, Lismore, NSW 2480, Australia
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  • Daniel L. E. Waters,

    1. Southern Cross Plant Science, Centre for Plant Conservation Genetics, Southern Cross University, Lismore, NSW 2480, Australia
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  • Russell F. Reinke,

    1. Industry and Investment NSW, Yanco Agricultural Institute, Yanco, NSW 2703, Australia
    2. EH Graham Centre for Agricultural Innovation, Charles Sturt University and Industry & Investment, Waga Waga, NSW 2650 Australia
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  • Robert J. Henry

    1. Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, St Lucia, Qld 4072, Australia
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  • This is the first report of incorporation of massively parallel sequencing and long-range PCR to discover new SNP variants in a specific target group of genes (starch-related genes) in rice as model plant.

(Tel +61 2 6620 3961; fax +61 2 6622 2080; email akhara10@scu.edu.au)

Summary

High-throughput sequencing of pooled DNA was applied to polymorphism discovery in candidate genes involved in starch synthesis. This approach employed semi- to long-range PCR (LR-PCR) followed by next-generation sequencing technology. A total of 17 rice starch synthesis genes encoding seven classes of enzymes, including ADP-glucose pyrophosphorylase (AGPase), granule starch synthase (GBSS), soluble starch synthase (SS), starch branching enzyme (BE), starch debranching enzyme (DBE) and starch phosphorylase (SPHOL) and phosphate translocator (GPT1) from 233 genotypes were PCR amplified using semi- to long-range PCR. The amplification products were equimolarly pooled and sequenced using massively parallel sequencing technology (MPS). By detecting single nucleotide polymorphism (SNP)/Indels in both coding and noncoding areas of the genes, we identified genetic differences and characterized the SNP/Indel variation and distribution patterns among individual starch candidate genes. Approximately, 60.9 million reads were generated, of which 54.8 million (90%) mapped to the reference sequences. The average coverage rate ranged from 12 708 to 38 300 times for SSIIa and SSIIIb, respectively. SNPs and single/multiple-base Indels were analysed in a total assembled length of 116 403 bp. In total, 501 SNPs and 113 Indels were detected across the 17 starch-related loci. The ratio of synonymous to nonsynonymous SNPs (Ka/Ks) test indicated GBSSI and isoamylase 1 (ISA1) as the least diversified (most purified) and conservative genes as the studied populations have been through cycles of selection. This report demonstrates a useful strategy for screening germplasm by MPS to discover variants in a specific target group of genes.

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