Phosphorylation of tobacco eukaryotic translation initiation factor 4A upon pollen tube germination.
Eukaryotic translation initiation factor eIF-4A is a member of the DEAD box family of RNA helicases and RNA-dependent ATPases. In tobacco, eIF-4A is encoded by a gene family with one isoform, eIF-4A8, being exclusively expressed in pollen. This pollen-specific isoform is a candidate for mediating translational control in the developing gametophyte. Here we show that eIF-4A is barely phosphorylated in mature pollen, but during pollen tube germination, two isoforms of eIF-4A become phosphorylated. Phosphoamino acid analysis indicated phosphorylation of threonine. In order to determine whether pollen-specific eIF-4A8 is among the phosphorylated isoforms, we raised transgenic tobacco plants overexpressing eIF-4A8 containing a histidine tag. Hereby, we could show that indeed eIF-4A8 is modified through phosphorylation. The biological relevance of the phosphorylation of eIF-4A is discussed.
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Institute of Plant Physiology, University of Berne, Altenbergrain 21, CH-3013 Berne, Switzerland.
Kuhlemeier
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D015153:Blotting, Western; D015180:Electrophoresis, Gel, Two-Dimensional; D039601:Eukaryotic Initiation Factor-4A; D010448:Peptide Initiation Factors / Q000235:genetics / Q000378:metabolism*; D019606:Phosphoamino Acids / Q000032:analysis; D010766:Phosphorylation; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D011058:Pollen / Q000254:growth & development / Q000378:metabolism*; D011233:Precipitin Tests; D011994:Recombinant Proteins / Q000378:metabolism; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism
D010448:Peptide Initiation Factors; D019606:Phosphoamino Acids; D011994:Recombinant Proteins; D039601:Eukaryotic Initiation Factor-4A