serial passage mutant
DNA was fragmented using a Covaris microTUBETM (Covaris, Inc., MA) before constructing the DNAseq library with KAPA Library Preparation Kits (Kapa Biosystems Inc., MA). After adaptors were ligated to the sheared genomic DNA, fragments that were 400 to 800 bp in length were used for sequencing, with library amplification performed using eight PCR cycles.