Molecular studies of the Medicago truncatula MtAnn3 gene involved in root hair deformation

The full-length annexin gene, MtAnn3, of Medicago truncatula was cloned by 5＇ RACE. Compared with typical annexins, which contain a head domain and four homologous repeats in the conserved core domain, the MtAnn3 protein has only one repeat in the core domain. MtAnn3 can bind cell membranes when transiently expressed in onion epidermal cells. Agrobacterium rhizogenes-mediated transformation of MtAnn3 into Medicago roots revealed that overexpression of the gene can change the polarity of root hair growth in Ca^2＋-free medium. The plant hormone cytokinin was able to upregulate the expression of MtAnn3. While MtAnn3 transcripts were detected in young nodules, expression was not nodule-specific, and could be detected at high levels in the roots, stems and leaves as well.