sublong: Long Read Aligner

VerifiedSafe

Align long reads (e.g., PacBio, Oxford Nanopore) to a reference genome using Subread's long-read aligner, optionally in RNA-seq mode.

Sby Skills Guide Bot
Data & AIIntermediate
107/23/2026
Claude Code
#bioinformatics#long-read-alignment#subread#fastq#genomics

Recommended for

Our review

Aligns long FASTQ reads (PacBio, Oxford Nanopore) to a reference genome using Subread's long-read aligner, optionally in RNA-seq mode.

Strengths

  • Optimized for long sequencing reads
  • Supports RNA-seq mode with the -X flag
  • Outputs BAM or SAM files suitable for downstream analysis

Limitations

  • Requires a full single-block Subread index
  • Input format limited to FASTQ (or gzipped)
  • The -h flag does not display help correctly
When to use it

Use sublong when you need to align long reads (PacBio, ONT) to a reference genome and produce BAM or SAM output.

When not to use it

Avoid sublong if your reads are short or if you have a multi-block index, as it is not designed for those scenarios.

Security analysis

Safe
Quality score90/100

The skill only documents safe, standard bioinformatics commands (sublong alignment). No destructive actions, data exfiltration, or obfuscated payloads. The tool is a local executable, and usage is limited to alignment tasks.

No concerns found

Examples

Basic long-read alignment
Align the long reads in long_reads.fastq.gz to the index named long_index using sublong with 8 threads, outputting BAM to aligned.bam.
RNA-seq mode alignment
Run sublong in RNA-seq mode (-X) to align isoform reads from isoform_reads.fastq.gz against the transcriptome index transcriptome_index, output BAM to isoforms.bam with 8 threads.
SAM output format
Align long_reads.fastq.gz to index long_index using sublong and output in SAM format (not BAM) to aligned.sam.

name: sublong description: Use when aligning long FASTQ reads to a reference genome with Subread's long-read aligner, optionally in RNA-seq mode. disable-model-invocation: true user-invocable: true

sublong

Quick Start

  • Command: sublong -i <index_name> -r <input.fastq> -o <output.bam>
  • Local executable: /home/vimalinx/miniforge3/envs/bio/bin/sublong
  • Full reference: See references/help.md

When To Use This Tool

  • Aligning long reads (e.g., PacBio, Oxford Nanopore) to a reference genome
  • Mapping reads against a full Subread index with a single block
  • Producing BAM or SAM output for downstream analysis
  • RNA-seq mode alignment via the -X flag

Common Patterns

# Align long genomic reads and write BAM output
sublong -i long_index -r long_reads.fastq.gz -o long_reads.bam -T 8
# Run in long-read RNA-seq mode
sublong -i transcriptome_index -r isoform_reads.fastq.gz -o isoform_reads.bam -X -T 8
# Emit SAM instead of BAM
sublong -i long_index -r long_reads.fastq.gz -o long_reads.sam --SAMoutput

Recommended Workflow

  1. Build a full one-block Subread index first, usually via subread-buildindex -F -B.
  2. Prepare long reads in FASTQ or gzipped FASTQ format.
  3. Decide whether you want standard genomic alignment or RNA-seq mode with -X.
  4. Run sublong with an explicit output file and thread count.
  5. Validate the BAM or SAM output before downstream quantification, QC, or variant analysis.

Guardrails

  • The index must be a full index with exactly one block; multi-block indexes are not supported
  • Input must be FASTQ or gzipped FASTQ; other formats are not accepted
  • Default output is BAM; use --SAMoutput explicitly if SAM format is required
  • -h is not a true help switch here. Local testing shows --help and --version both print usage text and then complain about the unrecognized option; -v is the real version flag.
  • -o is mandatory for sublong; unlike some other Subread tools, output is not optional.
  • -X switches on RNA-seq mode but does not replace the need for an index compatible with the same reference build you expect downstream.
Related skills