Dominant-negative receptor uncovers redundancy in the Arabidopsis ERECTA leucine-rich repeat receptor-like kinase signaling pathway that regulates organ shape

Abstract

Arabidopsis ERECTA, a Leu-rich repeat receptor-like Ser/Thr kinase (LRR-RLK), regulates organ shape and inflorescence architecture. Here, we show that a truncated ERECTA protein that lacks the cytoplasmic kinase domain (ΔKinase) confers dominant-negative effects when expressed under the control of the native ERECTA promoter and terminator. Transgenic plants expressing ΔKinase displayed phenotypes, including compact inflorescence and short, blunt siliques, that are characteristic of loss-of-function erecta mutant plants. The ΔKinase fragment migrated as a stable ∼400-kD protein complex in the complete absence of the endogenous ERECTA protein and significantly exaggerated the growth defects of the null erecta plants. A functional LRR domain of ΔKinase was required for dominant-negative effects. Accumulation of ΔKinase did not interfere with another LRR-RLK signaling pathway (CLAVATA1), which operates in the same cells as ERECTA but has a distinct biological function. Both the erecta mutation and ΔKinase expression conferred a lesser number of large, disorganized, and expanded cortex cells, which are associated with an increased level of somatic endoploidy. These findings suggest that functionally redundant RLK signaling pathways, including ERECTA, are required to fine-tune the proliferation and growth of cells in the same tissue type during Arabidopsis organogenesis.