Partial silencing of the NEC1 gene results in early opening of anthers in Petunia hybrida
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O R I GI N A L P A P E R
Y.-X. Ge á G. C. Angenent á E. Dahlhaus á J. Franken J. Peters á G. J. Wullems á J. Creemers-Molenaar
Partial silencing of the NEC1 gene results in early opening of anthers in Petunia hybrida Received: 23 August 2000 / Accepted: 8 December 2000 / Published online: 28 February 2001 Ó Springer-Verlag 2001
Abstract The NEC1 gene, previously isolated from Petunia hybrida, is expressed at high levels in nectaries, and in a very localized fashion in stamens, particularly in the anther stomium cells and the upper part of the ®lament. To elucidate the function of the NEC1 gene, co-suppression was employed for down-regulation of NEC1 expression, and transposon insertion mutagenesis was used to knock out the NEC1 function. Among the transgenic plants and plants carrying dTph1 inserted in the NEC1 gene, an ``early open anther'' phenotype was observed. In this mutant phenotype, the anthers already open in young ¯ower buds (1.8 cm) that still contain immature pollen, resulting in poor pollen quality and impaired pollen release. The results obtained indicate that NEC1 might be involved in the development of stomium cells, which are ruptured during the normal process of anther dehiscence to release mature pollen. Southern analysis revealed the presence of a highly homologous NEC1-like gene, named NEC2, in the P. hybrida genome. The presence of NEC2 was con®rmed by segregation analysis and sequencing of genomic clones. The implications of these results and possible reasons why no visually obvious phenotype in nectaries could be produced by co-suppression or transposon insertion mutagenesis are discussed.
Communicated by G. Haughn Y.-X. Ge á G. C. Angenent á E. Dahlhaus á J. Franken J. Peters á J. Creemers-Molenaar (&) Plant Research International, Wageningen University and Research Center, P.O. Box 16, 6700 AA Wageningen, The Netherlands E-mail: [email protected] Tel.: +31-317-477131 Fax: +31-317-418094 G. J. Wullems Department of Molecular Plant Physiology, Catholic University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
Key words Nectary á Stomium á Gene silencing á Anther dehiscence á Petunia hybrida
Introduction Floral nectaries secrete nectar, a sugar-containing ¯uid that attracts pollinating insects. The molecular regulation of nectary development and nectar secretion is poorly understood. Recently, we cloned a new gene, NEC1, that appears to be involved in the process of nectar secretion (Ge et al. 2000). However, the exact function of NEC1 has not yet been elucidated. The NEC1 gene is highly expressed in nectaries of Petunia hybrida and weakly in stamens. In stamens, expression is con®ned to the anther stomium and the upper part of the anther ®lament (Ge et al. 2000). To elucidate the biological function of the NEC1 gene, we studied the eects on nectary and anther phenotypes of down regulation of NEC1 expression by co-suppression and of loss of function of NEC1 associated with transposon insertion mutagenesis. Inhibition of a speci®c gene by co-suppression
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