NEC1, a novel gene, highly expressed in nectary tissue of Petunia hybrida

To study the molecular regulation of nectary development, we cloned NEC1, a gene predominantly expressed in the nectaries of Petunia hybrida, by using the differential display RT-PCR technique. The secondary structure of the putative NEC1 protein is reminiscent of a transmembrane protein, indicating that the protein is incorporated into the cell membrane or the cytoplast m embrane. Immunolocalization revealed that NEC1 protein is present in the ne ctaries. Northern blot analyses showed that NEC1 is highly expressed in nec tary tissue and weakly in the stamen. GUS expression driven by the NEC1 pro moter revealed GUS activity in the outer nectary parenchyma cells, the uppe r part of the filament and the anther stomium. The same expression pattern was observed in Brassica napus. GUS expression was observed as blue spots o n the surface of very young nectaries that do not secrete nectar and do acc umulate starch. GUS expression was highest in open flowers in which active secretion of nectar and starch hydrolysis had taken place. Ectopic expressi on of NEC1 resulted in transgenic plants that displayed a phenotype with le aves having 3-4 times more phloem bundles in mid-veins than the wildtype Pe tunia. The possible role of NEC1 gene in sugar metabolism and nectar secret ion is discussed.