Figure 3.

Validation of vasculature-specific expression by northern blots and RT-PCR. A, Expression of four genes (PmMT1, PmMT2, PmRBCS1, and the contig P12.7.C1 [homologous to viral polyprotein]) in vascular (v) tissue isolated from leaves, in nonvascular (nv) tissue represented by petioles that had their vascular bundles extracted, and in intact petioles (p) was analyzed on northern blots. As expected, PmMT1 and PmMT2 are expressed almost exclusively in the vascular tissue, whereas expression of PmRBCS1 is higher in nonvascular tissue. Expression of P12.7.C1 is also highly specific for the vasculature. The bottom image represents the loading control (methylene blue-stained nylon filter). Gene names and accession numbers are given. B, Expression of 20 genes was analyzed in vascular (v) and nonvascular (nv) tissue. The figure shows the bands obtained by quantitative RT-PCR amplification with total RNA, the names of the respective genes (for novel genes the contig numbers are given), and their accession numbers. PmUBQ1 was used as a control that was expected to have similar expression levels in both tissues. PmPC1 (plastocyanine) was used as a control that was expected to be expressed mainly outside the vasculature. With the exception of PmQUA1, which shows comparable expression levels, all other genes are expressed mainly or exclusively in the vascular tissue.