Chapter 1 Scotti et al. (in prep) scaffolds preparation

The Guianan scaffolds from Scotti et al (in prep)…

1.1 Filtering scaffolds over \(1kbp\)

Because of the maybe poor quality of the assembly for scaffolds from Scotti et al (in prep), we first start by filtering scaffolds with a width superior to 1000 bp.

cd ~/Documents/BIOGECO/PhD/data/Symphonia_Genomes/Ivan_2018/
mkdir scf_1000
for scf in $( ls raw/ | grep scafSeq$); 
do
  echo item: $scf
  perl ~/Tools/SeqFilter/bin/SeqFilter -l 1000 raw/$scf --out scf_1000/$scf
done

1.2 Renaming

For all scaffolds we will use following code : **Ivan_2018_[file name without .scafSeq]_[scaffold name]**.

dir.create(file.path(path, "Ivan_2018", "renamed_scf_1000"))
files <- list.files(file.path(path, "Ivan_2018", "scf_1000"))
sapply(files, function(file){
  scf <- readDNAStringSet(file.path(path, "Ivan_2018", "scf_1000", file))
  names(scf) <- paste0("Ivan_2018_", gsub(".scafSeq", "", file), "_", gsub(" ", "_", names(scf)))
  writeXStringSet(scf, file.path(path, "Ivan_2018", "renamed_scf_1000",
                                 paste0(gsub(".scafSeq", "", file), ".1000.renamed.scafSeq")))
}, simplify = F)
unlink(file.path(path, "Ivan_2018", "scf_1000"), recursive = T)

1.3 Libraries merging

We will successively merge scaffolds from all libraries with quickmerge. We have 9 libraries resulting in 8 successive merge. We were only able to merge the 6 first libraries due to memory limiitation on my local machine and the absence of quickmerge on genotoul/genologin. We will still use this merging as a new reference.

cd ~/Documents/BIOGECO/PhD/data/Symphonia_Genomes/Ivan_2018/renamed_scf_1000
ref=(sympho47_1L1_002.1000.renamed.scafSeq merge1.fasta merge2.fasta merge3.fasta merge4.fasta merge5.fasta merge6.fasta merge7.fasta)
query=(sympho47_1L2_001.1000.renamed.scafSeq sympho47_2L1_008.1000.renamed.scafSeq sympho47_2L1_009.1000.renamed.scafSeq sympho47_2L1_010.1000.renamed.scafSeq sympho47_2L1_011.1000.renamed.scafSeq sympho47_2L1_012.1000.renamed.scafSeq sympho47_3L2_013.1000.renamed.scafSeq sympho47_4L1_014.1000.renamed.scafSeq)
for i in {0..7} 
do
  mkdir merge$i
  cp  "${ref[$i]}" "${query[$i]}" ./merge$i/
  cd merge$i
  nucmer -l 100 -prefix out ${ref[$i]} ${query[$i]}
  delta-filter -i 95 -r -q out.delta > out.rq.delta
  ~/Tools/quickmerge/quickmerge -d out.rq.delta -q ${query[$i]} -r ${ref[$i]} -hco 5.0 -c 1.5 -l n -ml m
  cd ..
  cp merge$i/merged.fasta ./merge$((i+1)).fasta
done

cd ~/Documents/BIOGECO/PhD/data/Symphonia_Genomes/Ivan_2018
mkdir merged_1000
cp  renamed_scf_1000/merge5/merged.fasta merged_1000/merged_1000.fa
cd merged_1000
makeblastdb -in merged_1000.fa -parse_seqids -dbtype nucl

1.4 Removing scaffolds with multimatch blasted consensus sequence from Torroba-Balmori et al. (unpublished)

We used the consensus sequence for French Guianan reads from Torroba-Balmori et al. (unpublished) previously assembled with ipyrad. As a first brutal approach we only keep the first sequence of the consensus loci file and transform it to fasta (see loci2fa.py script below). We then blast those consensus sequences on merged scaffolds from Scotti et al (in prep) with blastn in order to detect scaffolds with repetitive regions thanks to multimapped consensus sequences. Those sequences will be saved as a list to be removed in final selected scaffolds list.

infile = open("symphoGbS2.loci", "r")
outfile = open("symphoGbS2.firstline.fasta", "w")
loci = infile.read().split("|\n")[:-1]
for loc in loci:
    reads = loc.split("\n")
    name, seq = reads[0].split()
    print >>outfile, ">"+name+"\n"+seq
outfile.close()

cd ~/Documents/BIOGECO/PhD/data/Symphonia_Torroba/assembly/symphoGbS2_outfile
python loci2fa.py
cat symphoGbS2.firstline.fasta | tr - N >> symphoGbS2.firstline.fasta

cd ~/Documents/BIOGECO/PhD/data/Symphonia_Genomes/Ivan_2018
query=~/Documents/BIOGECO/PhD/data/Symphonia_Torroba/assembly/symphoGbS2_outfiles/symphoGbS2.firstline.fasta
blastn -db merged_1000/merged_1000.fa -query $query -out blast_consensus_torroba2.txt -evalue 1e-10 -best_hit_score_edge 0.05 -best_hit_overhang 0.25 -outfmt 6 -perc_identity 75 -max_target_seqs 10

blast <- read_tsv(file.path(path, "Ivan_2018", "blast_consensus_torroba2.txt"), col_names = F)
names(blast) <- c("Read", "Scaffold", "Perc_Ident", "Alignment_length", "Mismatches",
                  "Gap_openings", "R_start", "R_end", "S_start", "S_end", "E", "Bits")
write_file(paste(unique(blast$Scaffold), collapse = "\n"), 
           file.path(path, "Ivan_2018", "selected_scaffolds_blast_consensus2.list"))

seqtk subseq merged_1000/merged_1000.fa selected_scaffolds_blast_consensus2.list >> selected_scaffolds_blast_consensus2.fa

In total 542 scaffolds from Scotti et al (in prep) match consensus sequences from Torroba-Balmori et al. (unpublished). But several scaffolds obtained multiple matches that we cannot use for probes. We will thus exclude the whole scaffold if the scaffold is shorter than 2000 bp or the scaffold region matching the raw read if the scaffold is longer than 2000 bp.

Figure 1.1: Number of match with Torroba consensus reads vs gene width.

Table 1.1: Scaffold to cut due to multiple read match.

Scaffold	width	remove	cut
Ivan_2018_sympho47_2L1_012_scaffold197676__8.6	4993		4993-4932
Ivan_2018_sympho47_2L1_012_scaffold246452__6.6	3103		2980-3058
Ivan_2018_sympho47_2L1_012_scaffold26367__7.7	2168		2118-2168
Ivan_2018_sympho47_2L1_012_scaffold463128__4.7	2188		667-586
Ivan_2018_sympho47_2L1_008_scaffold309475__2.1	3525		342-292

Following scaffolds will be removed due to multitple matches and a length \(<200bp\): 2L1_012_scaffold645876__7.5, 2L1_012_scaffold176548__7.1, 2L1_012_scaffold21882__4.9, 2L1_012_scaffold9236__6.0. And other will be cut (see table 1.1).

1.5 Total filtered scaffolds