The FRT cassette present in P{His3.3B(FRT.His3.3B.WT.FLAG.ubiGFP)His3.3B.WT} has been excised (removing wild-type FLAG-tagged His3.3B sequences present within the cassette), allowing a wild-type untagged form of His3.3B to be expressed under the control of the His3.3B promoter.
His3.3BcHa rescues the sterility of His3.3AKO His3.3BKO double homozygous males.