Transcriptome of Frankia alni ACN14a under N-free culture in contact or not with a sub-inhibitory concentration of AgLTP24

To further investigate the role of nsLTPs in symbiosis, we investigated the function of non specific Lipid Tranfer protein (nsLTP) secreted by Alnus glutinosa in symbiosis with Frankia alni ACN14a and named as AgLTP24. Our previous work demonstrated that agltp24 gene was highly expressed in A. glutinosa from an early step of infection with F. alni ACN14a to the nodule. In planta, AgLTP24 is secreted at deformed root hair at the early step when the host recognized Frankia and targets the nitrogen-fixing vesicles of the symbiont inside the nodule cells. This previous work showed that AgLTP24 impact Frankia physiology by inhibiting cellular activity at 5µM and inhibiting nitrogen fixation at 100nM and above. As Frankia in the nodule is viable and has an active nitrogen fixation to provide nitrogen to the plant, here we investigated the molecular response of F. alni ACN14a under N-free conditions in contact or not with a sub-inhibitory concentration of AgLTP24 (1nM) using RNAseq method.