The ABCF3 Gene of Arabidopsis Is Functionally Linked with GCN1 but Not with GCN2 During Stress and Development

Abstract

One of the main mechanisms regulating translation is the one based on the phosphorylation of the alpha subunit of the translation initiation factor 2 (eIF2α) by the general control non-repressive 2 (GCN2) protein kinase. In yeast, this kinase binds to two scaffold proteins (GCN1 and GCN20), facilitating its activation on translating ribosomes. The homology of the three proteins exists in Arabidopsis. In this species, whereas the kinase is activated under several stress situations, the involvement of the scaffold proteins in those processes is controversial, and a new role for GCN1 in translation, independent of the phosphorylation of eIF2α, has been proposed. Arabidopsis presents five genes with homology to GCN20 (ABCF1 to 5) in its genome. We show here that any of these five genes is needed for eIF2α phosphorylation. Furthermore, plant phenotypes under abiotic stresses and chloroplast development suggest that ABCF3 is functionally linked with GCN1, but not with GCN2. Finally, gcn1 and abcf3 mutants share similar transcriptional reprogramming, affecting photosynthesis and stress responses. The common downregulation of regulators of the flagellin receptor FLS2 in both mutants suggest that the observed defect in pathogen-associated molecular pattern (PAMP)-induced stomatal closure of these two mutants could be mediated by these proteins.