Use of aphid stylectomy and RT-PCR for the detection of transporter mRNAs in sieve elements

Unmodified samples of barley (Hordeum vulgare) sieve tube sap have been obtained by severing the stylets (stylectomy) of feeding aphids and collecting the exuding liquid. Primers were designed to direct the amplification of a series of specific cDNAs encoding barley proteins selected because of their significance in sieve tube function. mRNA encoding the H+/sucrose co-transporter SUT1, a putative aquaporin and the H+/ATPase PPA1 were detected in sieve tube sap. These mRNA species appear to be present at very low concentrations. mRNA encoding the potassium transporter HAK1 could not be detected. The results strongly suggest that some mRNA species are imported into sieve elements, which are enucleate, from neighbouring companion cells.