Two titans finally meet each other under nitrogen deficiencies: FERONIA-TORC1 activation promotes plant growth

Abstract

Plant growth is determined by well-defined developmental processes that integrate cell-intrinsic factors and external environmental cues, and it is largely dependent on the assimilation of macro- and micro-nutrients from the environment. Between the macro-nutrients, the inorganic nitrogen (e.g., nitrate and ammonium) and amino acids are essential for plant survival and productivity. Beyond acting as macro-nutrients and structural components of macro-molecules, these nitrogen-containing molecules could also act as signaling molecules to orchestrate diverse genetic programs (Wang et al., 2018). Plant nutritional cues that rapidly change over time and space in the soils are tightly linked to signaling pathways that execute fast cellular programs to adjust to a challenging environment. Plant Rapid Alkalinization Factors (RALFs) are secreted peptides that function as extracellular signals and bind to Catharanthus roseus receptor-like kinase 1-like family members such as FERONIA (FER) (Liao et al., 2017). RALF1–FER complexes are central regulators of plant growth that allow plants to respond to environmental changes (Du et al., 2016; Zhu et al., 2020). This interaction triggers the recruitment of RPM1-induced protein kinase (RIPK) and the phosphorylation of both FER and RIPK in a mutually dependent manner (Du et al., 2016), followed by the recruitment and activation via phosphorylation of an early translation initiation factor (eIF4E1) (Zhu et al., 2020). These findings highlighted that the RALF1–FER–RIPK pathway is an important hub to control plant cell growth under specific conditions.