Detonate

Introduction

Quality evaulation of a de-novo transcriptome assembly from the creators of RSEM (Deweylab). It was designed to answer the shortcomings in the N50 score typically used to evaluate assembly. It is a much more comprehensive quality evaluation, requiring as input, no only the de-novo assembly, but all the raw reads that were used to assemble it.

Layout

Two main aspects to this program. Also included here are the executables associated

• rsem-eval
  1. rsem-eval-calculate-score
  2. rsem-eval-estimate-transcript-length-distribution
  3. rsem-plot-model
  4. rsem-build-read-index
  5. rsem-eval-run-em
  6. rsem-extract-reference-transcripts
  7. rsem-parse-alignments
  8. rsem-preref
  9. rsem-sam-validator
  10. rsem-scan-for-paired-end-reads
  11. rsem-simulate-reads
  12. rsem-synthesis-reference-transcripts

• ref-eval
  1. ref-eval
  2. ref-eval-estimate-true-assembly

Usage

The detonate module must be loaded beforehand

module load detonate

After de-novo assembly of your transcriptome, the first step is

rsem-eval-estimate-transcript-length-distribution <contigs.fasta> <outputld.txt>

Explanation:

• rsem-eval-estimate-transcript-length-distribution, a perl script
• <contigs.fasta>, your de-novo assembly
• <outputld.txt>, your chosen name for the output text file which will hold the mean and SD of the contig lengths distribution.

Next the RSEM-EVAL score can be calculated. There is one executable for this, and it has various options. Executing

rsem-eval-calculate-score --help

will allow you view them.

The standard usage example is:

rsem-eval-calculate-score -p 8 --transcript-length-parameters human.txt /data/reads.fq assembly1.fa assembly1_rsem_eval 76

Explanation: There are two option with an associated prefix: -p and --transcript-length-parameters. The rest are all positional

• -p 8, this refers to the number of threads the program run will use. In this case 8.
• --transcript-length-parameters, a filename contianing the output of the previous rsem-eval-estimate-transcript-length-distribution command.
• The next option is a comma separated list of the raw reads used to assemble the de-novo transcriptome in the first place. It's probably best to build a list of these files beforehand, and pass them as a subprocess with

  $(cat fq.lst |tr '\n' ',')

• the next option sis hte de-novo assembled fasta file
• the penultimate option in this example is the output prefix, a name (of the users choice) which will be used to prefix the output files.
• the final option is a number representing the length of the raw reads.

It's best to wrap this command in a job submission script as follows:

#!/bin/bash
#$ -V
#$ -cwd
#$ -j y
#$ -S /bin/bash
#$ -q highmemory.q
#$ -pe multi 8
module load detonate
rsem-eval-calculate-score -p $NSLOTS --transcript-length-parameters outputld.txt $(cat fq.lst |tr '\n' ',') <denovoassemblyname.fa> <output_prefix> <length_of_short_reads>

Links

• The published paper describing Detonate.
• source code webpage with some usage instructions