Differential regulation of a family of apyrase genes from Medicago truncatula

Four putative apyrase genes were identified from the model legume Medicago truncatula. Two of the genes identified from M. truncatula (Mtapy1 and Mtap y4) are expressed in roots and are inducible within 3 h after inoculation w ith Sinorhizobium meliloti. The level of mRNA expression of the other two p utative apyrases Mtapy2 and Mtapy3, was unaffected by rhizobial inoculation . Screening of a bacterial artificial chromosome library of M. truncatula g enomic DNA showed that Mtapy1, Mtapy3, and Mtapy4 are present on a single b acterial artificial chromosome clone. This apyrase cluster was mapped to Li nkage group seven. A syntenic region on soybean linkage group J was found t o contain at least two apyrase genes. Screening of nodulation deficient mut ants of M. truncatula revealed that two such mutants do not express apyrase s to any detectable level. The data suggest a role for apyrases early in th e nodulation response before the involvement of root cortical cell division leading to the nodule structure.