We isolated and characterized an Alnus glutinosa cDNA clone, pAg13, which corresponds to a gene expressed at higher levels in nodules induced by Frankia than in roots. The deduced polypeptide sequence is rich in glutamic acid and proline and contains a putative signal peptide indicating an extracellular location of Ag13. In situ hybridization showed that ag13 is expressed in the pericycle of the nodule vascular bundle and in infected cells that exhibited degradation of the endosymbiont.
Guan, C., Akkermans, A. D. L., van Kammen, A., Bisseling, T., & Pawlowski, K. (1997). ag13 is expressed in Alnus glutinosa nodules in infected cells during endosymbiont degradation and in the nodule pericycle. Physiologia Plantarum, 99, 601-607. https://doi.org/10.1034/j.1399-3054.1997.990412.x