UAS regulatory sequences drive expression of a mutated form of Hsap\RAC1 (carries a Q61L amino acid replacement) that is tagged at the N-terminal end with mCherry. The coding sequence is also tagged with Tag:AsLOV2, rendering the protein photoactivatable.
Photoactivation of Hsap\RAC1PA.Q61L.Scer\UAS.T:Disc\RFP-mCherry,T:Zzzz\PT1 in the centre of a single border cell (where its expression is under the control of Scer\GAL4slbo.2.6) has negligible effect on border cell cluster migration if the photoactivated cell is at the front of the border cell cluster. However, if the photoactivated cell is at the back of the border cell cluster, net cluster movement backwards is seen.
In the absence of illumination migration of border cells expressing Hsap\RAC1PA.Q61L.Scer\UAS.T:Disc\RFP-mCherry,T:Zzzz\PT1 under the control of Scer\GAL4slbo.2.6 is unperturbed.
Photoactivation of Hsap\RAC1PA.Q61L.Scer\UAS.T:Disc\RFP-mCherry,T:Zzzz\PT1 at the rear of border cell clusters expressing Hsap\RAC1PA.Q61L.Scer\UAS.T:Disc\RFP-mCherry,T:Zzzz\PT1 under the control of Scer\GAL4slbo.2.6 results in reverse border cell migration. When photoactivation is stopped, border cells stall for a variable period of time before regaining forward migration.
Border cell clusters expressing Rac1N17.Scer\UAS and Hsap\RAC1PA.Q61L.Scer\UAS.T:Disc\RFP-mCherry,T:Zzzz\PT1 under the control of Scer\GAL4slbo.2.6 in which Hsap\RAC1PA.Q61L.Scer\UAS.T:Disc\RFP-mCherry,T:Zzzz\PT1 has been activated by illumination in one cell do not show forward migration. However, photoactivation of Hsap\RAC1PA.Q61L.Scer\UAS.T:Disc\RFP-mCherry,T:Zzzz\PT1 in approximately half of the cluster results in slow forward movement.
In the absence of illumination, border cells expressing EgfrDN.Scer\UAS and PvrDN.Scer\UAS under the control of Scer\GAL4slbo.2.6 and carrying Hsap\RAC1PA.Q61L.Scer\UAS.T:Disc\RFP-mCherry,T:Zzzz\PT1 fail to move forward. When Hsap\RAC1PA.Q61L.Scer\UAS.T:Disc\RFP-mCherry,T:Zzzz\PT1 is photoactivated at the rear of the border cell cluster, rearward movement is seen. When photoactivation is stopped, the border cell cluster stops moving.