The PELOTA-HBS1 Complex Orchestrates mRNA Translation Surveillance and PDK1-mediated Plant Growth and Development

The quality control system for messenger RNA is fundamental for cellular activities in eukaryotes. To elucidate the molecular mechanism of 3-Phosphoinositide-Dependent Protein Kinase1 (PDK1), an essential regulator throughout growth and development of eukaryotes, a forward genetic approach was employed to screen for suppressors of the loss-of-function T-DNA insertional pdk1.1 pdk1.2 double mutant in Arabidopsis. Notably, the severe growth attenuation of pdk1.1 pdk1.2 is rescued by sop21 (suppressor of pdk1.1 pdk1.2) that harbours a loss-of-function mutation in PELOTA1 (PEL1). PEL1 is a homologue of mammalian PELOTA and yeast DOM34, which form a heterodimeric complex with the GTPase HBS1, responsible for ribosome rescue to assure the quality and fidelity of mRNA molecules. Genetic analysis further reveals that the dysfunction of PEL1-HBS complex fails to degrade the T-DNA-disrupted, truncated but functional PDK1 transcripts, thus rescuing pdk1.1 pdk1.2. Our studies demonstrate the functionality and identify the essential functions of a homologous PELOTA-HBS1 complex in higher plant, and provide novel insights into the mRNA quality control mechanism.