ALUMINUM-INDUCED GENES - INDUCTION BY TOXIC METALS, LOW-CALCIUM, AND WOUNDING AND PATTERN OF EXPRESSION IN ROOT-TIPS

We have investigated the response of four Al-induced genes (wali1, -3, -4, and -5) from wheat (Triticum aestivum L.) to other stresses. The relative transcript levels of wali1 (encoding a plant metallothionein- like protein), wali3 and wali5 (putative Bowman-Birk proteinase inhibi tors), and wali4 (phenylalanine ammonialyase) increased in root tips o f wheat after 2-d treatments with toxic levels of all other metals tes ted (Cd, Fe, Zn, Cu, Ga, In, and La). The expression levels of wali1, -3, -4, and -5 also increased in the root tips of plants grown in the presence of low levels of Ca (10 mu M). The transcript levels of wali1 , -3, and -5 increased in wounded leaf and root tissue, whereas the tr anscript levels of wali4 increased only in wounded leaves. The site of expression of wali1, -3, and -5 in root tips was identified using in situ hybridization. wali1 was expressed predominantly in the meristema tic tissue of the root tip, whereas wali3 and wali5 were expressed pre dominantly in the cortical tissue of the root. Some changes in the sit e of expression of these genes were evident in the roots of Al-treated plants.