Abstract
The plant-tumorigenic 6b (AK-6b) gene of Agrobacterium tumefaciens AKE10 induces morphological alterations of tobacco plants. AK-6b-seedlings featured their cotyledons with protrusions, and short, thick roots. These morphological alterations were accompanied with reduced auxin transport activity by the AK-6b gene. To understand the relationship between auxin distribution and morphological alterations in more detail, we applied the well-established auxin influx carrier inhibitor, 1-Naphthoxyacetic acid (NOA) to AK-6b-tobacco seedlings. Resulting auxin distribution was monitored by auxin-specific reporter gene construct DR5:GUS expression. In roots, both wild-type and AK-6b seedlings showed reduced number of lateral roots. In contrast, wild-type shoots were unaltered with NOA, but AK-6b shoots showed reduction of protrusions and newly emergence of outgrowths developed from hypocotyls. Histochemical GUS assay revealed that the staining of AK-6b shoots was localized to the protrusions and altered tissues. These results show that redistribution of auxin was accomplished by combination of AK-6b gene expression and NOA, and the AK-6b gene may act as an auxin efflux carrier inhibitor.
