A novel intracellular auxin transport mechanism in rice was revealed by researcher from Biotechnology Research Institute, CAAS.This research was published online on New Phytologist on June 6.

The plant hormone auxin plays a crucial role in plant growth and development. An appropriate content of auxin flowing across and present in cells is important for regulation of embryonic apical basal axis formation, postembryonic organogenesis, tropistic growth, apical dominance, abiotic and biotic stress responses, vascular development and senescence.

However, Little is known about the transport mechanism of intracellular auxin. Here, we report two vacuole-localized proteins, Oryza sativa OsCONTINUOUS VASCULAR RING-LIKE 1 (OsCOLE1) and OsCOLE1-INTERACTING PROTEIN (OsCLIP), that regulate intracellular auxin transport and homoeostasis.

Overexpression of OsCOLE1 markedly increased the internode length and auxin content of the stem base, whereas these parameters were decreased in RNA interference (RNAi) plants. OsCOLE1 was localized on the tonoplast and preferentially expressed in mature tissues. We further identified its interacting protein OsCLIP, which was co-localized on the tonoplast.

protein binding assays demonstrated that the N-terminus of OsCOLE1 directly interacted with OsCLIP in yeast cells and the rice protoplast. Furthermore, 3H-indole-3-acetic acid (3H-IAA) transport assays revealed that OsCLIP transported IAA into yeast cells, which was promoted by OsCOLE1.

The results indicate that OsCOLE1 affects rice development by regulating intracellular auxin transport through interaction with OsCLIP, which provides a new insight into the regulatory mechanism of intracellular transport of auxin and the roles of vacuoles in plant development. This novel auxin metabolism process deepens our understanding of the molecular mechanisms of auxin metabolism in plant cells.

This research was supported by the National Natural Science Foundation of China and Maize Functional Genomics Research and Application. The first author is Dr. Fei Liu and correspondence author is Lei Wang.