EXPRESSION OF AN AUXIN-REGULATED AND CYTOKININ-REGULATED GENE IN CAMBIAL REGION IN ZINNIA

The expression patterns of a cDNA clone, p48h-10, of an auxin-induced gene were examined in isolated mesophyll cells of Zinnia and in the or gans of Zinnia plants. In the isolated mesophyll cells, the mRNA accum ulates in 48 hr of culture with 1-naphthaleneacetic acid alone. Becaus e the first cell division occurs before 36 hr of culture, the gene pro bably is not involved in cell division. Benzyladenine does not induce expression of this gene, but the combination of 1-naphthaleneacetic ac id and benzyladenine induces the mRNA accumulation about 24 hr earlier than does 1-naphthaleneacetic acid alone. Tissue print hybridization shows that the mRNA is present predominantly in the cambial region in stems,leaves, and roots and in the vascular bundles in flower buds but does not occur in the apical regions of shoot or root. The characteri stics of the gene expression, including auxin- and cytokinin-regulated induction and cambial region localization, encourage us to suggest th at the gene is involved in the early process of vascular differentiati on.