Enzymic Reaction and Gene Expression of Endo-Xyloglucan Transferase

• Published in: Journal of Applied Glycoscience Vol. 42; no. 2; pp. 169 - 175
• Main Authors: OKAMOTO, Shigehisa, TOMITA, Etsuko, NISHITANI, Kazuhiko
• Format: Journal Article
• Language: English; Japanese
• Published: The Japanese Society of Applied Glycoscience 1995; 日本応用糖質科学会
• ISSN: 1340-3494; 1884-4898
• DOI: 10.11541/jag1994.42.169

Xyloglucans are the major component of plant cell wall matrix. Cellulose microfibrils are crosslinked by xyloglucans to form an interwoven network structure of the cell wall. The cleavage and reconnection of xyloglucan cross-links is required for rearrangement of the network structure of the cell wall, an essential process for cell growth and differentiation in plants. Endo-xyloglucan transferase (EXT) is a newly identified class of transferase that catalyzes "molecular grafting" between xyloglucan cross-links in the cell wall. Based on the amino acid sequence information of the purfie EXT protein, cDNAs encoding EXT proteins were cloned from azuki bean and four other plant species. Northern blot analyses have disclosed that the gene expression of EXT is closely correlated with cell growth in stems of azuki bean seedlings. To elucidate the regulatory mechanism of the EXT gene expression in the bean plants, we analyzed the effects of plant hormones and sucrose on the EXT-RNA levels in the stem sections. We found that auxin and gibberellin increased the EXT-mRNA levels in the sections within 2 hr. Sucrose application, which enhanced wall deposition, also increased the EXTmRNA level. These results suggest involvement of EXT in both cell expansion and cell wall deposition in plants.