CHARACTERIZATION OF THE AtPNP RECEPTOR AND NATRIURETIC PEPTIDES XacPNP AND AtPNP-A.

DI PAOLO, V.; MASOTTI, F.; VRANYCH, CV; GARAVAGLIA, B.S.; GOTTIG, N.; JORGELINA OTTADO

Rosario

Congreso; LVI SAIB Meeting; 2020

Plant natriuretic peptides (PNP) are peptide hormones essential in homeostasis responses. These include concentrationdependentpromotion of stomatal opening, rapid and transient increases in cellular cGMP levels, modulation of K+, Na+ andH+ net ion fluxes, and increases in osmoticum-dependant H2O uptake into protoplasts. The best PNP characterized isArabidopsis thaliana PNP, AtPNP-A. It interacts with a leucine-rich repeat (LRR) protein, denominated AtPNPR, which iscapable of catalyzing the conversion of guanosine triphosphate to cGMP. AtPNPR was in silico predicted to be located in theplant cell membrane being responsible for cGMP-dependent signaling once AtPNP-A is bound to its amino terminal LRRdomain. Therefore, AtPNP-A is able to trigger different responses to adapt to changes in the environment and in this way,regulate internal homeostasis, and it does so by the interaction with AtPNPR. Xanthomonas citri subsp. citri, the bacterialpathogen responsible for citrus canker, has a PNP-like protein (XacPNP), whose gene was probably acquired in a horizontalgene transfer event. XacPNP shares significant sequence similarity with AtPNP-A, mostly in the active region of AtPNP-A,which is also sufficient for the interaction of AtPNP-A with AtPNPR. Previous results of our group support the hypothesisthat bacterial XacPNP behaves as AtPNP-A in modulating plant homeostasis. It mimics the host protein in elicitingphysiological responses in plants similar to AtPNP-A, such as stomatal opening and increases in net water flux. Anotherproperty is that the presence of XacPNP sustains photosynthesis during pathogen infection. Thus, we propose that XacPNP isable to interact with AtPNPR as AtPNP-A to exert its function. In this context, first we determined that both natriuretic peptidesinteract with AtPNPR in plant tissues by bimolecular fluorescence complementation (BifC) and we also observed that XacPNPhelps in keeping Arabidopsis tissue in a better condition during biotic stress and this is dependent on the presence of thereceptor. Further, we expressed the aforementioned proteins as GFP-protein fusions in order to locate them in the plant tissueand determine their interaction dynamics. Overall, our results put forward that XacPNP interacts with AtPNPR as AtPNP-Adoes and that the signalling of the response depends on this receptor.