Characterization of an Endo-p-l,4-Glucanase Gene lnduced by Auxin in Elongating Pea Epicotyls'

A gene (EGLI) encoding an endo-p-l,4-~-glucanase (EGase, EC 3.2.1.4) of pea (Pisum sativum) has been cloned and characterized. EGL 1 encodes a 486-amino acid polypeptide, including a 24-mer putative signal peptide. The mature protein has a calculated molecular mas of 51.3 kD and an isoelectric point of 9.1. This pea ECase shares significant similarity with ECases from other plant species, but it appears to be distinct from the EGases associated with abscission and fruit ripening. Although EGL7 transcripts are detected in all parts of pea plants, they are relatively abundant in flowers and young pods undergoing rapid growth and most abundant in elongating epicotyls of etiolated seedlings. When epicotyl segments (6 mm long, 4 mm from the apical hook) are incubated in a 5 p~ solution of the synthetic auxin analog 2,4-dichlorophenoxyacetic acid, the concentration of EGL7 mRNA increases about 1 O-fold when the segments elongate most rapidly.