Characterization of the Heat-Stable Proteome during Seed Germination in Arabidopsis with Special Focus on LEA Proteins.

Orarat Ginsawaeng,Joachim Kopka,Alexander Erban,Michal Gorka,Aleksandra Skirycz,Carolin Heise,Dirk K Hincha,Franziska Brueckner,Rainer Hoefgen,Ellen Zuther

doi:10.3390/ijms22158172

Abstract

During seed germination, desiccation tolerance is lost in the radicle with progressing radicle protrusion and seedling establishment. This process is accompanied by comprehensive changes in the metabolome and proteome. Germination of Arabidopsis seeds was investigated over 72 h with special focus on the heat-stable proteome including late embryogenesis abundant (LEA) proteins together with changes in primary metabolites. Six metabolites in dry seeds known to be important for seed longevity decreased during germination and seedling establishment, while all other metabolites increased simultaneously with activation of growth and development. Thermo-stable proteins were associated with a multitude of biological processes. In the heat-stable proteome, a relatively similar proportion of fully ordered and fully intrinsically disordered proteins (IDP) was discovered. Highly disordered proteins were found to be associated with functional categories development, protein, RNA and stress. As expected, the majority of LEA proteins decreased during germination and seedling establishment. However, four germination-specific dehydrins were identified, not present in dry seeds. A network analysis of proteins, metabolites and amino acids generated during the course of germination revealed a highly connected LEA protein network.

Highlights

Seeds are the desiccation-tolerant life stage of most plant species
Seed germination is a complex process, which is accompanied by comprehensive changes and a concerted action of molecular players represented by gene expression, protein abundance and metabolite levels
Dry seeds with a quiescent metabolic state undergo a transition to proliferative metabolic state for plant propagation [22]

Summary

Introduction

Seeds are the desiccation-tolerant life stage of most plant species. Seedlings lose their desiccation tolerance during the early stages of germination [1,2,3]. Phase I consists of a rapid uptake of water which allows the initiation of metabolic activity, such as protein synthesis from stored mRNAs. During Phase II, further water uptake is limited. In Phase III, referred to as the post-germination phase, water uptake increases again and seedling development is observed. This includes cell division, elongation of the radicle and mobilization of stored reserves to fuel seedling development before plants become photoautotrophic. After emergence of the radicle, seedling establishment progresses by emergence of hypocotyl and cotyledons and a new growth stage begins with the full opening of the cotyledons [7]

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