A Kruppel-like zinc finger protein is involved in nitrogen-fixing root nodule organogenesis

Mechanisms regulating plant host differentiation of the nitrogen-fixing roo t nodules remain mostly unknown. Sinorhizobium meliloti induces this proces s in Medicago sativa in which the Mszpt2-1 gene is expressed in vascular bu ndles of roots and nodules. This gene codes for a Kruppel-like zinc finger protein, a class of transcription factors involved in many animal developme ntal processes. Expression of Mszpt2-1 in yeast cells conferred osmotic tol erance. Antisense plants grew normally but developed nonfunctional nodules, in which differentiation of the nitrogen-fixing zone and bacterial invasio n were arrested. Hence, a vascular bundle-associated Kruppel-like gene is r equired for the formation of the central nitrogen-fixing zone of the root n odule.