ANTISENSE EXPRESSION OF THE PEPTIDE-TRANSPORT GENE ATPTR2-B DELAYS FLOWERING AND ARRESTS SEED DEVELOPMENT IN TRANSGENIC ARABIDOPSIS PLANTS

Previously, we identified a peptide transport gene, AtPTR2-B, from Ara bidopsis thaliana that was constitutively expressed in all plant organ s, suggesting an important physiological role in plant growth and deve lopment. To evaluate the function of this transporter, transgenic Arab idopsis plants were constructed expressing antisense or sense AtPTR2-B . Genomic Southern analysis indicated that four independent antisense and three independent sense AtPTR2-B transgenic lines were obtained, w hich was confirmed by analysis of the segregation of the kanamycin res istance gene carried on the T-DNA. RNA blot data showed that the endog enous AtPTR2-B mRNA levels were significantly reduced in transgenic le aves and Glowers, but not in transgenic roots. Consistent with this re duction in endogenous AtPTR2-B mRNA levels, all four antisense lines a nd one sense line exhibited significant phenotypic changes, including late flowering and arrested seed development. These phenotypic changes could be explained by a defect in nitrogen nutrition due to the reduc ed peptide transport activity conferred by AtPTR2-B. These results sug gest that AtPTR2-B may play a general role in plant nutrition. The AtP TR2-B gene was mapped to chromosome 2, which is closely linked to the restriction fragment length polymorphism marker m246.