Abstract:

The Arabidopsis gene UPRIGHT ROSETTE (URO) was previously identified as a leaf developmental regulator, as all rosette leaves of the semi-dominant upright rosette (uro) mutant grow uprightly at seedling stages. Here, we report more detailed phenotypic characterizations of the uro mutant and show that the URO gene has multiple functions in plant development. In addition to its aberrant leaf-growing pattern, the uro mutant displayed pleiotropic phenotypes. Both uro/+ and uro/uro plants showed a loss of apical dominance, while such a phenotype in the uro/uro plants appeared more severe. Some secondary branches of the uro/uro plants were replaced by leaves, for which petioles were attached to the abaxial side of leaves. Flowers often exhibited varying abnormalities, with altered numbers of petals and stamens and abnormally fused organs. Stems of the uro mutant were soft, which was caused by lacking interfascicular fiber. In addition, vascular differentiation in mutant stem was delayed. The loss of apical dominance and the defects in vascular development and interfascicular fiber formation suggest that the URO function might be associated with auxin-mediated plant development. To provide more direct evidence whether the URO is involved in auxin action, we examined the URO function in auxin polar transportation pathway by analyzing pinformed1 (pin1) uro double mutant. Phenotypes of the double mutant suggest that URO and PINFORMED1 (PIN1) have partial genetic interactions in plant development, which further supports the hypothesis that the URO gene may play an important role in the auxin regulatory pathway.

Key words: Arabidopsis , auxin, interfascicular fiber, pinformed1, upright rosette