Isolation and promoter analysis of two genes encoding different endo- -1,4-glucanases in the non-climacteric strawberry1

Two endo-beta-1,4-glucanase (EGase; EC 3.2.1.4.) genes, highly expressed during ripening of the non-climacteric strawberries (Fragariaxananassa Duch. cv. Chandler), were isolated. Serial promoter deletions of both genes (i.e. FaEG1 and FaEG3) fused to GUS were transiently assayed in strawberry fruits by using a technique recently developed in this laboratory. Although differences were observed with the short fragments, GUS activity became comparable with the largest fragments of both promoters. The apparently similar strength of the two largest promoter fragments was in contrast with previous results of Northern analyses which demonstrated different transcripts amounts for the two genes. The inclusion of the 3' flanking region of both genes in the transient assays showed that, in the case of FaEG3, the 3' region had a down-regulating effect on the expression of GUS, and this might account for the lower amount of FaEG3 mRNA usually observed in ripe fruits compared to that of FaEG1. Downstream instability elements might be involved in such down-regulation.