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  • How to annotate the multiploid plant using pacbio cDNA sequencing?

    I want to do the transcriptome annotiation for wheat, which is a hexapliod plant. Since there has no reference genome sequence now, we are going to sequence using pacbio RNA-seq to get the full length isoform sequences as many as possible. I have four samples and have sequenced using HiSeq 2000, then I am going to do the pacbio RNA-seq. So should I do the sequcing combined all samples together or just sequencing seperately? Is there any influence with my hexaploid wheat data analysis? BTW, should I using the IsoSeq pipline or the PacBioToCA/LSC error correction pipline?

    Thanks a lot O(∩_∩)O~
    happy

  • #2
    This paper on wheat Iso-Seq just published btw, think you may be interested in how they did it:
    Background The large and complex hexaploid genome has greatly hindered genomics studies of common wheat (Triticum aestivum, AABBDD). Here, we investigated transcripts in common wheat developing caryopses using the emerging single-molecule real-time (SMRT) sequencing technology PacBio RSII, and assessed the resultant data for improving common wheat genome annotation and grain transcriptome research. Results We obtained 197,709 full-length non-chimeric (FLNC) reads, 74.6 % of which were estimated to carry complete open reading frame. A total of 91,881 high-quality FLNC reads were identified and mapped to 16,188 chromosomal loci, corresponding to 13,162 known genes and 3026 new genes not annotated previously. Although some FLNC reads could not be unambiguously mapped to the current draft genome sequence, many of them are likely useful for studying highly similar homoeologous or paralogous loci or for improving chromosomal contig assembly in further research. The 91,881 high-quality FLNC reads represented 22,768 unique transcripts, 9591 of which were newly discovered. We found 180 transcripts each spanning two or three previously annotated adjacent loci, suggesting that they should be merged to form correct gene models. Finally, our data facilitated the identification of 6030 genes differentially regulated during caryopsis development, and full-length transcripts for 72 transcribed gluten gene members that are important for the end-use quality control of common wheat. Conclusions Our work demonstrated the value of PacBio transcript sequencing for improving common wheat genome annotation through uncovering the loci and full-length transcripts not discovered previously. The resource obtained may aid further structural genomics and grain transcriptome studies of common wheat.


    They used the FLNC reads (from Iso-Seq classify) and did error correction with Illumina using proovread. I think any of the following can work: running Iso-Seq only (classify + cluster) and using Illumina for quantification and validation only, using hybrid approach (LSC or proovread)...

    If you already have Iso-Seq setup I would suggest first getting the Iso-Seq pipeline run through. Then if you have additional bandwidth you can try running the hybrid approaches. I think LSC may rely pretty heavily on a good ref genome so you may want to be aware of that. Iso-Seq (and I think proovread as well) are both completely de novo.

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