|Samac, Deborah - Debby|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/4/2005
Publication Date: 4/4/2005
Citation: Liu, J., Miller, S.S., Graham, M., Bucciarelli, B., Catalano, C.M., Sherrier, D.J., Samac, D.A., Ivashuta, S., Fedorova, M., Matsumoto, P., Gantt, J.S., Vance, C.P. 2005. Root nodule specific calmodulin-like proteins; co-opting genes for symbiosis. 2nd Australian Model Legume Workshop Proceedings, April 5-8, 2005, Rottnest Island, Western Australia. p. 13.
Technical Abstract: Legume-rhizobia symbiotic nitrogen (N2) fixation plays a critical role in sustainable N management in agriculture and in Earth’s N cycle. Signaling between rhizobia and legumes initiates development of a unique plant organ, the root nodule, where the bacteria undergo endocytosis and become surrounded by a plant membrane to form a symbiosome (Sym). Between this membrane and the encased bacteria there exists a matrix-filled space (the symbiosome space, SymS) that is thought to contain a mixture of plant- and bacterially-derived proteins and about which little is known. Maintenance of the symbiosis state requires continuous communication between the plant and bacterial partners. Here we show in the model legume Medicago truncatula (Mt) that a novel family of six calmodulin-like proteins (CaMLs) are expressed specifically in root nodules, are localized within the SymS, and are required for effective symbiosis. All six nodule-specific CaML genes are clustered in the Mt genome along with two other nodule-specific genes, nodulin-22 and nodulin-25. Sequence comparisons and phylogenetic analysis suggest that an unequal recombination event occurred between nodulin-25 and a nearby calmodulin (CaM) gave rise to the first CaML and the gene family evolved by tandem duplication and divergence. The data provide striking evidence for the co-opting of a ubiquitous Ca2+-binding gene for symbiotic purposes.