The Arabidopsis AtEPR1 extensin-like gene is specifically expressed in endosperm during seed germination

Screening of 10 000 Arabidopsis transgenic lines carrying a gene-trap (GUS) construct has been undertaken to identify markers of seed germination. One of these lines showed GUS activity restricted to the endosperm, at the mic ropylar end of the germinating seed. The genomic DNA flanking the T-DNA ins ert was cloned by walking PCR and the insertion was shown to be located 70 bp upstream of a 2285 bp open reading frame (AtEPR1) sharing strong similar ities with extensins. The AtEPR1 open reading frame consists of 40 proline- rich repeats and is expressed in both wild-type and mutant lines. The expre ssion of the AtEPR1 gene appears to be under positive control of gibberelli c acid, but is not downregulated by abscisic acid during seed germination. No expression was detected in organs other than endosperm during seed germi nation. The putative role of AtEPR1 is discussed in the light of its specif ic expression in relation to seed germination.