A 'pYtag' phospho-tyrosine tag cassette has been inserted into the endogenous tor locus, at the C-terminal end of the coding sequence. This sequence acts as a biosensor for activation of the tor receptor tyrosine kinase (RTK). The pYtag cassette consists of three copies of the Tag:ITAM(hCD3E) tag, a P2A sequence and the Clover fluorescent protein tagged with Tag:ZtSH2. The 3xTag:ITAM(hCD3E) tag is incorporated at the C-terminal end of the tor protein, while the P2A sequence promotes the separate translation of the Clover-Tag:ZtSH2 reporter. In the absence of tor activation, the Tag:ZtSH2-tagged Clover reporter is located in the cytosol. Upon activation of the tor RTK, phosphorylation of tyrosine residues in Tag:ITAM(hCD3E) results in this tag binding to Tag:ZtSH2, recruiting the Tag:ZtSH2-tagged Clover reporter to the membranes where tor is activated. A Disc\RFP^{DsRed(T1).3xP3.cHa} marker (flanked by termini from the Tni\piggyBac transposable element) has also been inserted, downstream of the pYtag sequence cassette.