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cDNA clones encoding 1,3-beta-glucanase and a fimbrin-like cytoskeletal protein are induced by Al toxicity in wheat roots

Cruz-Ortega, R., Cushman, J.C., Ownby, J.D.
Plant physiology 1997 v.114 no.4 pp. 1453-1460
Triticum aestivum, Brassica napus, Arabidopsis thaliana, Hordeum vulgare, Nicotiana tabacum, Pisum sativum, roots, aluminum, phytotoxicity, protein synthesis, actin, molecular weight, isoelectric point, beta-glucanase, cytoskeleton, protein composition, genetic code, complementary DNA, genes, gene expression, clones, cultivars, genetic variation, amino acid sequences, messenger RNA, stress response
A cDNA library made from mRNA of Al-treated roots of an Al-sensitive wheat (Triticum aestivum cv Victory) cultivar was screened with a degenerate oligonucleotide probe derived from the partial amino acid sequence of the Al-induced protein TAl-18. Of seven clones that initially hybridized with the probe, one encoded a novel 1,3-beta-glucanase having a calculated molecular weight of 46.3 and an isoelectric point of 6.0. Like the A6 1,3-beta-glucanase gene products from Brassica napus and Arabidopsis thaliana, the predicted wheat protein had a C-terminal extension with three potential glycosylation sites. Northern analysis revealed that wheat 1,3-beta-glucanase mRNA was up-regulated in Al-intoxicated roots, with highest expression after 12 h. The antibody to A6 1,3-beta-glucanase from B. napus cross-reacted with a 56-kD protein that was induced after 24 h. A second partial cDNA clone showed similarity to genes encoding cytoskeletal fimbrin-like (actin-bundling) proteins. Althoughwell studied in animals and fungi, fimbrins have not previously been described in plants. Fimbrin-like transcripts were up-regulated after 24 h of Al treatment in the Al-sensitive wheat cv Victory. In the Al-tolerant cv Atlas 66, fimbrin-like mRNA was up-regulated within 12 h by Al concentrations that did not inhibit root growth. Cellular stress associated with Al toxicity therefore causes up-regulation of a defense-related gene and a gene involved in the maintenance of cytoskeletal function.