The LaCEP1 peptide modulates cluster root morphology in Lupinus albus

Abstract

White lupin cluster roots are specialized brush-like root structures that are formed in some species under phosphorus (P)-deficient conditions. They intensely secrete protons and organic acid anions for solubilization and acquisition of sparingly soluble phosphates. Phytohormones and sucrose modulate cluster root number, but the molecular mechanisms of cluster root formation have been elusive. Here, a novel peptide phytohormone was identified that affects cluster root development. It belongs to the C-TERMINALLY-ENCODED PEPTIDE (CEP) family. Members of that family arrest root growth and modulate branching in model species. LaCEP1 was highly expressed in the pre-emergence zone of clusters. Over-expression of the gene encoding the LaCEP1 propeptide resulted in moderate inhibition of cluster root formation. The primary and lateral root lengths of lupin were little affected by the overexpression, but LaCEP1 reduced cluster rootlet and root hair elongation. Addition of a 15-mer core peptide derived from LaCEP1 similarly altered root morphology and modified cluster activity, suggesting that a core sequence of the propeptide is functionally sufficient. Stable overexpression in Arabidopsis confirmed the LaCEP1 function in root growth inhibition across species. Taken together, the root inhibitory effects of the LaCEP1 phytohormone suggest a role as of a regulatory module involved in cluster root development in white lupin.

Root Handling Affects Carboxylates Exudation and Phosphate Uptake of White Lupin Roots

“…auxin, nitric oxide), sucrose and miRNAs ( e.g. miR399) ( Liu and Vance, 2010 ; Wang et al., 2015 ; Uhde-Stone, 2017 ; Zhou et al., 2019 ). Additionally, cluster roots can be also formed in plants with sufficient P nutrition, although those cluster roots are not fully functional ( Meng et al., 2013 ; Wang et al., 2015 ).…”

A prion-like protein regulator of seed germination undergoes hydration-dependent phase separation

“…Square ($1cm) leaf segments were cut from tobacco leaves transiently expressing 35S:FLOE1-GFP or 35S:YFP-FLAG, and incubated for 15 minutes in either 1 M NaCl to induce plasmolysis (Zhou et al, 2019) or water (control). Cell walls were stained by supplementing the solutions with propidium iodide (Thermo Fisher Scientific) at a final concentration of 10 mg/mL.…”

ABCG transporters export cutin precursors for the formation of the plant cuticle

“…Nevertheless, all ABCG transporters were at least partially localized at the PM based on the co-localization of the FP-tagged ABCGs with the PM-marker PIP2A-mCherry expressed under the CaMV-35S promoter as well as their localization adjacent the propidium-iodine-stained cell wall (Figure S4). 42,43 FP-labeled proteins, PIP2A-mCherry as well as the FP-labeled ABCGs, were often additionally localized to the ER, in particular when the expression level was high (Figure S4), probably due to saturation of the secretion system.…”