A αTub84B promoter drives expression of wts that has been mutated to carry a R708A amino acid substitution (mutation of a residue predicted to be essential for mats protein binding), and which is tagged at the N-terminal end with Citrine and at the C-terminal end with mTFP1. Generated by excision of the FRT cassette in wtsR708A.αTub84B.FRT.CWT.