Effect of increased IAA synthesis in root nodule of Medicago plants

In plants auxin modulates diverse processes such as tropic response to light and gravity, general root and shoot growth and vascular development. IAA (indol-3-acetic acid) is produced largely in shoot apex. Auxin is transported basipetally in shoots, while both acropetal (in the central cylinder) and basipetal (via epidermaland cortical cells) transport occur in roots [4]. Most Rhizobacteria synthesize IAA, and in symbiotic Rhizobia have been identified different auxin biosyntheticpathways. It has been proposed that IAA plays a role in nodule formation, and it has been also demonstrated that nodulated roots have a phytormone content higherthan root tissue [1]. Sinorhizobium meliloti induces nodule formation in Medicago species; S. meliloti 1021 has been engineered by introducing promintron-iaaM-tms2gene construct (S. meliloti 1021 IAA), which increases auxin content in the nodules.