Five genes induced by aluminum in wheat (Triticum aestivum L.) roots.

Five different cDNAs (termed wali1 to wali5 for Wheat Aluminum Induced) whose expression was induced by Al stress have been isolated from the root tips of Al-treated wheat (Triticum aestivum L.) plants. Four of these genes were induced 24 to 96 h after Al treatment, and their expression is reduced when the Al is removed. Each of these four genes was induced by inhibitory levels of Al in two wheat cultivars--Warigal, an Al-sensitive cultivar, and Waalt, an Al-tolerant cultivar. The fifth gene (wali2) showed a complex bimodal pattern of induction and was induced by Al only in the sensitive cultivar. Comparison of the nucleotide sequences of these clones to those in the sequence data bases showed that wali4 is homologous to phenylalanine ammonia-lyase and wali1 is homologous to a group of plant proteins that are cysteine-rich and have homology to metallothioneins. wali2 encodes a novel protein with a repeating motif of cysteine amino acids. The remaining two wali clones (wali3 and wali5) encode related, cysteine-rich proteins that show no significant homology to any known sequences.