Sequence labels are strings of text following a greater-than (>)
symbol at the start of a line in a FASTA
file. The label is terminated by the end of the line.
Labels are truncated at the first white space symbol (blank or
tab) unless the -notrunclabels option is
specified. This is designed to save memory, as some databases (notably,
the NCBI NR protein database) have very long labels.
See also: size annotations.