GA-independent DELLA regulation by inositol pyrophosphate in a nonvascular land plant

Abstract

DELLA proteins integrate external and internal cues into a signaling network critical for land plant survival. In flowering plants, gibberellins (GAs) induce DELLA recognition to its receptor GID1, resulting in the polyubiquitylation and degradation of DELLA repressors. Notably, bryophytes lack the canonical GA receptor, despite the presence of genes encoding DELLA in these nonvascular land plants. Consequently, the underlying molecular mechanisms of DELLA regulation in bryophytes have remained largely elusive. Here, we report that MpVIH, responsible for the synthesis of inositol pyrophosphate messenger InsP₈, negatively regulates DELLA in the liverwort Marchantia polymorpha to promote cell division and thallus development. Mechanistically, we elucidate that MpVIH-derived InsP₈ binds to MpDELLA, promoting polyubiquitination and proteasomal degradation of the repressor. Lastly, our study provides evidence for the conservation of inositol pyrophosphate-controlled DELLA degradation in angiosperms. We, thus, identify a 'noncanonical' type of DELLA regulation by the inositol pyrophosphate messengers in land plants.