A single phosphorylation event alters root behavior

Siao et al. demonstrate that single phosphorylation on a protein alters root behavior in Arabidopsis.

By Wei Siao and Eugenia Russinova, VIB-UGent Center for Plant Systems Biology

Background: Plant roots react to their environment by using hormone signaling pathways, which enable their cells to respond to external cues such as gravity and soil properties. Endocytosis is a cellular process in which membrane proteins or other external substances are internalized, and it can affect hormone signaling and cell communication. Therefore, changes in endocytosis can impact how a plant root responds to external stimuli. Understanding the role of endocytosis in plant root behavior can be useful in developing effective strategies to improve plant root growth and enhance nutrient-seeking behavior in the soil.

Questions: Is there a mechanism that can regulate components of the endocytic machinery? Can phosphorylation, a post-translational modification, be involved in this process?

Findings: ADAPTOR-ASSOCIATED PROTEIN KINASE 1 (AAK1) phosphorylates the medium subunit of the Adaptor Protein-2 complex (AP2M), on a single amino acid residue. Mutations in the AAK1 gene or preventing AP2M phosphorylation in Arabidopsis alter the root gravitropism and touch response to hard surfaces. Introducing a phospho-mimic form of AP2M into an aak1 mutant restored the altered root behavior to the wild-type level. Our findings show that a single phosphorylation event on AP2M by AAK1 can alter root behavior while maintaining normal plant growth and development.

Next steps: Scientists are working to decode the complex behavior of roots in order to enhance their ability to adapt to different and changing soil environments. Future studies will investigate how endocytosis coordinates different signaling pathways involved in various root tropisms, as well as identify new regulators of endocytosis that can affect root behavior.

Reference:

Wei Siao, Peng Wang, Xiuyang Zhao, Lam Dai Vu, Ive De Smet, and Eugenia Russinova. (2023) Phosphorylation of ADAPTOR PROTEIN-2 μ-adaptin by ADAPTOR-ASSOCIATED KINASE1 regulates the tropic growth of Arabidopsis roots. https://doi.org/10.1093/plcell/koad141