Characterization and accumulation pattern of an mRNA encoding an abscission-related beta-1,4-glucanase from leaflets of Sambucus nigra.

A cDNA library was produced using mRNA extracted from ethylene-treated leaflet abscission zones of common elder (Sambucus nigra). Screening of the library with the insert from pBAC10, which encodes an abscission beta-1,4-glucanase (cellulase) from bean (Phaseolus vulgaris), resulted in the isolation of a near-full-length cDNA which was designated JET 1. Northern analysis, using JET 1 as a probe, detected a transcript of 1.9 kb that accumulated prior to the first visible signs of cell separation. Accumulation of the JET 1 transcript is promoted by ethylene and primarily restricted to the tissue comprising the abscission zone. Sequence analysis of JET 1 indicates it is 1768 bp in length and shares significant homology at the amino acid level with beta-1,4-glucanases from the leaf abscission zone of P. vulgaris (67%) and ripening avocado fruit (48%). The predicted peptide sequence of the S. nigra enzyme contains two potential glycosylation sites. Genomic Southern analysis of S. nigra DNA reveals that JET 1 may belong to a multi-gene family.