Expression of a membrane-anchored endo-1,4-β-glucanase from Brassica napus, orthologous to KOR from Arabidopsis thaliana, is inversely correlated to elongation in light-grown plants

A PCR fragment derived from a membrane-anchored endo-1,4-β-glucanase cDNA was amplified using degenerated oligonucleotides and mRNA from oilseed rape (Brassica napus L.) siliques. Sequence analysis of the corresponding gene, Cel16, showed that the predicted Cel16 protein has high identity with the Arabidopsis KOR protein (94%). High-stringency genomic Southern analysis further revealed that Cel16 and KOR are most likely orthologous genes performing a similar function in both species. Northern blot and GUS analysis of transgenic Arabidopsis containing a fusion between a 2.0 kb Cel16 promoter fragment and the GUS reporter gene showed that Cel16 was expressed at a low level in the primary raceme, the young lateral stems, the elongation zone of the primary root and the older root base. By contrast, a high level of Cel16 mRNA accumulation was found in the young root and in the main stem carrying flowers and young siliques. Cel16 transcripts were localized to the apical meristem, cambium, primary xylem and cortex of oilseed rape stem tissue by in situ RT-PCR. A similar pattern of activity was found in the GUS analysis of transgenic Arabidopsis.