Arabidopsis Plant Natriuretic Peptide Is a Novel Interactor of Rubisco Activase

Abstract

Plant natriuretic peptides (PNPs) are a group of systemically acting peptidic hormones affecting solute and solvent homeostasis and responses to biotrophic pathogens. Although an increasing body of evidence suggests PNPs modulate plant responses to biotic and abiotic stress, which could lead to their potential biotechnological application by conferring increased stress tolerance to plants, the exact mode of PNPs action is still elusive. In order to gain insight into PNP-dependent signalling, we set out to identify interactors of PNP present in the model plant Arabidopsis thaliana, termed AtPNP-A. Here, we report identification of rubisco activase (RCA), a central regulator of photosynthesis converting Rubisco catalytic sites from a closed to an open conformation, as an interactor of AtPNP-A through affinity isolation followed by mass spectrometric identification. Surface plasmon resonance (SPR) analyses reveals that the full-length recombinant AtPNP-A and the biologically active fragment of AtPNP-A bind specifically to RCA, whereas a biologically inactive scrambled peptide fails to bind. These results are considered in the light of known functions of PNPs, PNP-like proteins, and RCA in biotic and abiotic stress responses.

Amino acid motifs for the identification of novel protein interactants

“…Other candidate PNP interactors have also since been experimentally validated. They include the Arabidopsis thaliana catalase 2 CAT2 (TAIR: At4g35090) and a Rubisco activase RCA (At2g39730), and in both cases, they harbor amino acid motifs similar to PNP-R1 that can be used to further guide the search PNP-protein interactions [108] , [109] , [110] . The ongoing discoveries of the growing PNP-interactome is one recent example that demonstrates the capability of motif searches in informing and supporting experimental elucidation of candidate ligands and/or interactors.…”

“…The PNP-binding site (green), the ABA-binding site (blue), and the H-NOX center (orange) are represented, with the key amino acids involved in interactions with their ligands shown in dark grey. The PNP-binding site is implicated in H 2 O 2 homeostasis, regulation of protoplast volume, defense response against pathogens, and photosynthesis, which could be achieved through interactions of PNP-A (TAIR: At2g18660) with PNP-receptor 1 (TAIR: At1g33612), catalase 2 (TAIR: At4g35090) or Rubisco activase (TAIR: At2g39730) [106] , [107] , [108] , [109] , [110] . The ABA-binding site of an outward rectifying potassium channel AtGORK (TAIR: At5g37500) is involved in K + transport in guard cells [95] .…”

Thriving on half: low nutritional demand in Stephanopodium engleri involves adjustments in photosynthetic apparatus functionality

“…Different proteins are involved in redox regulation, photosynthesis (RubisCO), ATP-dependent carboxylation and chaperone [16]. Rubisco activase (RCA) enables the release of the inhibitory sugar phosphates from the active site of Rubisco, thereby sustaining Rubisco in its active state and continuing ribulose-1,5-bisphosphate substrate regeneration, which is a critical factor in photosynthesis [17]. Under N-de cient conditions, senescence of leaves is accelerated mainly due to degradation of Rubisco proteins [18].…”