TileSeqs: Form a Set of Tiles for Each Group of Sequences.

Description

Creates a set of tiles that represent each group of sequences in the database for downstream applications.

Usage

TileSeqs(dbFile, tblName = "DNA", identifier = "", minLength = 26, maxLength = 27, maxTilePermutations = 10, minCoverage = 0.9, add2tbl = FALSE, verbose = TRUE, ...)

Arguments

dbFile

A SQLite connection object or a character string specifying the path to the database file.

tblName

Character string specifying the table of sequences to use for forming tiles.

identifier

Optional character string used to narrow the search results to those matching a specific identifier. If "" then all identifiers are selected.

minLength

Integer providing the minimum number of nucleotides in each tile. Typically the same or slightly less than maxLength.

maxLength

Integer providing the maximum number of nucleotides in each tile. Tiles are designed primarily for this length, which should ideally be slightly greater than the maximum length of oligos used in downstream functions.

maxTilePermutations

Integer specifying the maximum number of tiles in each target site.

minCoverage

Numeric providing the fraction of coverage that is desired for each target site in the group. For example, a minCoverage of 0.9 request that additional tiles are added until 90% of the group is represented by the tile permutations.

add2tbl

Logical or a character string specifying the table name in which to add the result.

verbose

Logical indicating whether to display progress.

...

Additional arguments to be passed directly to SearchDB.

Value

A data.frame with a row for each tile, and multiple columns of information. The row_names column gives the row number. The start, end, start_aligned, and end_aligned columns provide positioning of the tile in a consensus sequence formed from the group. The column misprime is a logical specifying whether the tile meets the specified constraints. The columns width and id indicate the tile's length and group of origin, respectively.The coverage field gives the fraction of sequences containing the tile in the group that encompass the tile's start and end positions in the alignment, whereas groupCoverage contains the fraction of all sequences in the group containing a tile at their respective target site. For example, if only a single sequence out of 10 has information (no gap) in the first alignment position, then coverage would be 100% (1.0), while groupCoverage would be 10% (0.1).The final column, target_site, provides the sequence of the tile.

Details

TileSeqs will create a set of overlapping tiles representing each target site in an alignment of sequences. The most common tile permutations are added until the desired minimum group coverage is obtained. The dbFile is assumed to contain DNAStringSet sequences (any U's are converted to T's).

Target sites with one more more tiles not meeting a set of requirements are marked with misprime equals TRUE. Requirements include minimum group coverage, minimum length, and maximum length. Additionally, tiles are required not to contain more than four runs of a single base or four di-nucleotide repeats.

Examples

Run this code

db <- system.file("extdata", "Bacteria_175seqs.sqlite", package="DECIPHER")
tiles <- TileSeqs(db, identifier="Pseudomonas")