A POLLEN-SPECIFIC DEAD-BOX PROTEIN RELATED TO TRANSLATION INITIATION-FACTOR EIF-4A FROM TOBACCO

A pollen-specific sequence, NeIF-4A8, has been isolated from a cDNA li brary from mature pollen of Nicotiana tabacum cv. Samsun. NeIF-4A8 is a full-length cDNA whose deduced amino acid sequence exhibits high hom ology to the eucaryotic translation initiation factor eIF-4A from mous e, Drosophila and tobacco. eIF-4A is an RNA helicase which belongs to the supergene family of DEAD-box proteins. Northern blot analysis with a gene-specific probe showed strict anther-specific expression of NeI F-4A8 starting at microspore mitosis. With antibodies raised against t obacco eIF-4A the presence of abundant eIF-4A-related proteins in deve loping anthers and pollen grains was demonstrated. The genomic analysi s shows that the coding region is split by three introns whereas a lar ge, fourth intron is situated in the 5'-untranslated region. A promote r construct with 2137 bp of upstream sequence fused to the GUS reporte r gene was used to confirm that the expression is confined to the hapl oid cells within the anther. NeIF-4A8 is a prime candidate for mediati ng translational control in the developing male gametophyte.