A useful protocol for in situ RT-PCR on plant tissues.

This study describes an effective method of in situ RT-PCR (RT-ISPCR) that was developed to localize gene expression in plant tissues. This RT-PCR technique was performed on sectioned tissues of female buds of the cucumber GY3 inbred line. The CUS1 gene, encoding the MADS-box type (agamus-like) protein, the expression pattern of which was described earlier, was used as a marker gene for optimisation of steps in the in situ RT-PCR inside the cells. For the identification of RT-PCR products inside the cells of the female buds, they were fixed in FAA solution, embedded in Paraplast Plus and cut into 7 microm thick sections which were dewaxed by immersion in HistoClear and dehydrated with ethanol. They were washed in water, then in 0.02M HCl, 2xSSC and PBS buffer. In the next step of tissue pretreatment, the sections were digested with 1% pectinase. As shown, the pectinase treatment proved to be a crucial step in the tissue preparation procedure to get successful RT-PCR products. After washing in PBS buffer, the sections were digested with protease K followed by incubation with RNase-free DNase I, and subsequently washed in 2xSSC, 1xSSC and 0.5xSSC and finally in DEPC-treated water. Then the sections were covered with 50 microl of the RT-PCR reaction mixture supplemented with 0.5 microM digoxigenin dUTP and sealed with a coverslip. After amplification in situ the PCR products were identified with anti-digoxigenin antibody (Roche Molecular Biochemicals), conjugated with alkaline phosphatase. The data obtained showed that specific signals reflecting CUS1 gene expression were detected in the female flower buds of cucumber. The specificity of the in situ RT-PCR protocol was confirmed by dot blot hybridization of RT-PCR products with CUS1 cDNA probe.