Promoter activity of a putative pollen monosaccharide transporter in Petunia hybrida and characterisation of a transposon insertion mutant.
For the growth of the male reproductive cells of plants, the pollen, the presence of sufficient sucrose or monosaccharides is of vital importance. From Petunia hybrida a pollen-specific putative monosaccharide transporter designated PMT1 (for petunia monosaccharide transporter) has been identified previously. The present work provides an in-depth analysis and characterisation of PMT1 in the context of pollen development with the GUS reporter gene and an insertion mutant. The promoter of the pollen-specific putative PMT1 gene has been isolated by inverse PCR and sequenced. Analysis of plants transformed with the promoter-GUS fusion confirmed the specificity of this gene, belonging to the late pollen-specific expressed genes. GUS activity was detected even after 24 h of in vitro pollen germination, at the pollen tube tip. To elucidate the importance of PMT1 for gametophyte development and fertilisation, we isolated a mutant plant containing a transposon insertion in the PMT1 gene by the dTph1 transposon-tagging PCR-based assay. The PMT1 mutant contained a dTph1 insertion in position 1474 bp of the transcribing part of the gene, before the last two transmembrane-spanning domains. Analysis of the progeny of the heterozygous mutant after selfing revealed no alterations in pollen viability and fertility. Mature pollen grains of a plant homozygous for the transposon insertion were able to germinate in vitro in a medium containing sucrose, glucose, or fructose, which indicates that PMT1 is not essential for pollen survival. Several explanations for these results are discussed in the present work.
Garrido
D
D
Department of Cell Biology, Centre for Plant Breeding and Reproduction Research, Dienst Landbouwkundig Onderzoek, Plant Research International, Wageningen. dgarrido@ugr.es
Busscher
J
J
van Tunen
A J
AJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D004251:DNA Transposable Elements / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics; D018525:Germination / Q000502:physiology; D005966:Glucuronidase / Q000378:metabolism; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009154:Mutation / Q000235:genetics; D032306:Petunia / Q000235:genetics* / Q000502:physiology; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011058:Pollen / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*
D004251:DNA Transposable Elements; D009004:Monosaccharide Transport Proteins; D010940:Plant Proteins; D005966:Glucuronidase