Plant Molecular Biology 34: 837–842, 1997. 837 c 1997 Kluwer Academic Publishers. Printed in Belgium. Cloning and characterization of elongation specific endo-1,4- -glucanase (cel1) from Arabidopsis thaliana Ziv Shani, Mara Dekel, Galit Tsabary and Oded Shoseyov The Kennedy Leigh Centre for Horticultural Research and The Otto Warburg Center for Agricultural Biotechnology. The Faculty of Agriculture, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel. ( author for correspondence) Received 9 July 1996; accepted in revised from 25 February 1997 Key words: elongation, gene expression, glucanase, Arabidopsis thaliana Abstract The isolation of an elongation-specific endo-1,4- -glucanase-cel1 from Arabidopsis thaliana was made possible by the fact that considerable homology exists between different endo-1,4- -glucanase (EGase) genes from different plants. Degenerate primers were synthesized based on two conserved regions from the avocado and tomato cellulase amino acid sequences. The A. thaliana cel1 cDNA gene was found to encode a 54 kDa protein; sequence comparison with the avocado EGase revealed 56% identity.Northern blot analysis of cel1 suggested its developmental regulation. RNA transcripts were undetectable in fully expanded leaves as well as at the basal internode of flowering stems. However, a strong transcript signal was detected in the elongating zone of flowering stems of normal plants. The RNA transcript level of cel1 in the elongating zone of dwarf flowering stems was significantly lower than in the corresponding zone in normal plants. This suggests cel1’s involvement in cell elongation in A. thaliana. Transgenic tobacco plants transformed with the putative cel1 promoter region fused to the gus reporter gene, showed a significant GUS staining both in shoot and root elongating zones. These results further substantiate the link between cel1 expression and plant cell elongation. Introduction The plant cell elongation mechanism is a fundamen- tal process with primary importance in plant-tissue development. Cell elongation requires relaxation of the rigid primary cell wall [2, 5, 10, 26]. Several mecha- nisms for this relaxation have been suggested, includ- ing the activities of endoxyloglucan transferase [25], xyloglucan endotransglycosylase [11] and expansins [24]. EGase has been suggested to play an important role in the elongation process [29, 34]. Substantional evidence for the involvement of a 1,3-1,4- -glucan- specific enzyme in cell elongation was found in mono- cotyledons [13, 17, 18]. EGase has been implicated in xyloglucan degradation during vegetative growth and fruit ripening [14, 15]. The activity of this enzyme The nucleotide sequence data reported will appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession numbers X98543 and X98544. could affect the generation of oligosaccharins, signal- ing molecules that are involved, among other things, in plant development and cell elongation (see for review [6]). Most of the EGase genes isolated to date have been studied in relation to fruit ripening [3, 9, 23, 31] and abscission zones [21, 32, 33]. More recent- ly, Wu et al. [36] cloned the EGase gene from pea and showed its expression to be induced by auxin in elongating epicotyls. In the present work we describe the cloning and characterization of elongation-specific EGase (cel1) from A. thaliana. Materials and methods Plant material and isolation of plant nucleic acids Arabidopsis thaliana cv. Columbia and Nicotiana tabaccum-SR1 plants were grown at 24 C under