# Can I run STAR without an annotation file?

I wish to use Rascaf to scaffold a fragmented draft genome.

For this, I need to provide a BAM file of aligned RNA-seq reads and the draft genome.

So, I indexed the draft genome with STAR like this:

STAR --runMode genomeGenerate --genomeDir output/index --genomeFastaFiles draft.fa


Then, I tried to aligned the reads like this:

STAR --genomeDir output/index --readFilesIn reads.fastq.gz --readFilesCommand gunzip -c --outFileNamePrefix output/alignment --quantMode GeneCounts --outSAMunmapped None --outSAMtype BAM SortedByCoordinate --outSAMattrRGline ID:RG1 CN:yy \"DS: z z z\" SM:sample


The latter commands outputs the following error:

Transcriptome.cpp:51:Transcriptome: exiting because of *INPUT FILE* error: could not open input file exonGeTrInfo.tab
Solution: check that the file exists and you have read permission for this file
SOLUTION: utilize --sjdbGTFfile /path/to/annotantions.gtf option at the genome generation step or mapping step


It suggests I should use a GTF file. But this is a draft genome of an individual for which no GTF is available. I could try to adapt a GTF from a close relative but for the scaffolding, it seems superfluous. Is there a way I can map with STAR without the GTF?

These commands were run on a GNU/Linux machine.

I don't think you can use the --quantMode GeneCounts option with no annotations. I think the error is trying to look for an exon file generated from the annotations to do the quantitation on. Remove that and I think it should work, as the manual specifically states that annotations are optional but highly recommended.