The diageotropica mutation alters auxin induction of a subset of the Aux/IAA gene family in tomato

The diageotropica (dgt) mutation has been proposed to affect either auxin p erception or responsiveness in tomato plants. It has previously been demons trated that the expression of one member of the Aux/IAA family of auxin-reg ulated genes is reduced in dgt plants. Here, we report the cloning of ten n ew members of the tomato Aux/IAA family by PCR amplification based on conse rved protein domains. All of the gene family members except one (LeIAA7) ar e expressed in etiolated tomato seedlings, although they demonstrate tissue specificity (e.g. increased expression in hypocotyls vs. roots) within the seedling. The wild-type auxin-response characteristics of the expression o f these tomato LeIAA genes are similar to those previously described for Au x/IAA family members in Arabidopsis. In dgt seedlings, auxin stimulation of gene expression was reduced in only a subset of LeIAA genes (LeIAA5, 8, 10 , and 11), with the greatest reduction associated with those genes with the strongest wild-type response to auxin. The remaining LeIAA genes tested ex hibited essentially the same induction levels in response to the hormone in both dgt and wild-type hypocotyls. These results confirm that dgt plants c an perceive auxin and suggest that a specific step in early auxin signal tr ansduction is disrupted by the dgt mutation.