Dynamics of liquid-liquid phase separation of wheat gliadins

Adeline Boire,Adeline Boire,Adeline Boire,Adeline Boire,Minne Paul Lettinga,Paul Menut,Paul Menut,Paul Menut,Paul Menut,Paul Menut,Paul Menut,Christian Sanchez,Marie-Hélène Morel,Marie-Hélène Morel,Marie-Hélène Morel

doi:10.1038/s41598-018-32278-5

Abstract

During wheat seeds development, storage proteins are synthetized and subsequently form dense protein phases, also called Protein Bodies (PBs). The mechanisms of PBs formation and the supramolecular assembly of storage proteins in PBs remain unclear. In particular, there is an apparent contradiction between the low solubility in water of storage proteins and their high local dynamics in dense PBs. Here, we probe the interplay between short-range attraction and long-range repulsion of a wheat gliadin isolate by investigating the dynamics of liquid-liquid phase separation after temperature quench. We do so using time-resolved small angle light scattering, phase contrast microscopy and rheology. We show that gliadins undergo liquid-liquid phase separation through Nucleation and Growth or Spinodal Decomposition depending on the quench depth. They assemble into dense phases but remain in a liquid-like state over an extended range of temperatures and concentrations. The analysis of phase separation kinetics reveals that the attraction strength of gliadins is in the same order of magnitude as other proteins. We discuss the respective role of competing interactions, protein intrinsic disorder, hydration and polydispersity in promoting local dynamics and providing this liquid-like behavior despite attractive forces.

Highlights

Most plant seeds have the unique ability to naturally store large reservoirs of proteins in a stable and compact environment for extended periods
We showed that gliadin dispersions remain in a liquid-like state at 20 °C for concentrations as high as 450 g/L revealing a net repulsion in the condensed system[27]
We investigated the kinetics of phase separation of wheat gliadins using Time-resolved small-angle light scattering (TR-SALS), phase contrast microscopy and rheology

Summary

Introduction

Most plant seeds have the unique ability to naturally store large reservoirs of proteins in a stable and compact environment for extended periods. There is an apparent contradiction between their very low solubility in water suggesting strong attractive properties and their high local dynamics in dense PBs, suggesting a peculiar equilibrium of protein-protein and protein-solvent interactions To tackle this question, we use an in vitro approach probing the phase behaviour of a wheat storage proteins isolate to infer their interaction properties as done for lysozyme[13,14,15], lens proteins[16,17,18] or casein micelles[19,20]. We choose to work on monomeric gliadins extractible from mature seeds as a representative protein mixture at the time of PBs formation Another challenge is to choose the appropriate solvent to probe the interaction properties of wheat storage properties. We discuss the biological significance of these results in the framework of PBs formation

Methods

Findings

Discussion

Conclusion