The unifying power of stress: Bringing together mRNAs and proteins

Increasing temperatures, as well as the expanding salinization of arable soils cause severe yield losses in agricultural production every year. In the course of global climate changes, these negative effects become more severe. This creates increasingly more pressure on plant breeders and farmers to keep the yield high under harsher conditions. To generate yield-efficient varieties under these circumstances, it is crucial to understand the molecular processes which mediate heat and salt-resistance in plants.

How does a plant react to heat or salt stress on the molecular level?

Upon sudden heat or salt stress, the plant cell immediately restructures its mRNA and protein metabolism. The regulation of the mRNA pool is executed partially by the formation of microscopically visible mRNA-protein aggregates (mRNPs), also known as stress granules. The recruitment of mRNAs into mRNPs withdraws them from the translational machinery, thereby ensuring that only proteins which are indispensable for the plant cell survival are produced. Simultaneously, the sorting and degradation of proteins via endosomal structures is adapted. This process is regulated by highly conserved protein complexes named ESCRT and ensures the stress-specific degradation of proteins in the plant cell.

Synchronization of protein production and protein degradation

Recent research results of our group showed that a key protein of the ESCRT-dependent protein degradation machinery interacts with mRNP-specific proteins. Furthermore, a stress-dependent recruitment of this particular ESCRT-protein to newly formed stress granules was observed (Figure 1). This indicates a connection between the two cellular processes. A spatial and functional linkage of mRNPs and ESCRT would provide an elegant mechanism to coordinate protein production and protein degradation.
We are interested in answering the following questions by using cell biology, molecular and biochemical methods: Is the key ESCRT protein inactivated by the relocalization to mRNPs thereby suppressing ESCRT-dependent protein degradation? Does the ESCRT protein exert a new, so far unknown molecular function in mRNPs? Or do the protein interactions of mRNP and ESCRT proteins cause a spatial association of the two compartments? Answering these questions may enable us to understand how the bulk flow of stress-relevant mRNAs and proteins is regulated, which in turn can be utilized to adapt crop plants for harsher life conditions in the future.

Contribution by Heike Wolff, WG Hülskamp, Botanical institute, University Cologne

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Planter’s Punch

Under the heading Planter’s Punch we present each month one special aspect of the CEPLAS research programme. All contributions are prepared by our young researchers.

Heinrich Heine University
University of Cologne
Max Planck Institute for Plant Breeding Research
Forschungszentrum Jülich