Promotes Growth, Meristem, Seed, and Vein Formation during Rice Plant Development.

The plant hormone auxin acts as a mediator providing positional instructions in a range of developmental processes. Studies in L. show that auxin acts in large part via activation of Auxin Response Factors (ARFs) that in turn regulate the expression of downstream genes. The rice ( L.) gene is of interest because of its expression in developing rice organs and its high sequence similarity with , a gene with prominent roles in development. We have assessed the phenotype of homozygous insertion mutants in the gene and found that in relation to wildtype, seedlings produced fewer and shorter roots as well as shorter and less wide leaves. Leaves developed fewer veins and larger areoles. Mature plants had a reduced root system, fewer branches per panicle, fewer grains per panicle and fewer filled seeds. Mutants had a reduced sensitivity to auxin-mediated callus formation and inhibition of root elongation, and phenylboronic acid (PBA)-mediated inhibition of vein formation. Taken together, our results implicate in auxin-mediated growth of multiple organs and leaf veins. also appears to play a central role in the formation of lateral root, panicle branch, and grain meristems.