Boosting crop productivity

Phytohormones coordinate plant growth and development and, as such, are key to food production. For a phytohormone to be fully functional, there are several points in its production line when arabinose sugar is added (arabinosylation). Identifying enzymes that modify hormones could help in the synthesis of active signalling peptides for use as agricultural tools.

The EXHOMO (Glycosylation of peptide hormones and extensins from the model plant Arabidopsis thaliana and in-vitro synthesis of glycosylated peptides) project has looked at two peptide hormones, PSY1 and CLV3. The researchers also followed the biochemical fate of the hormones as they pass through the cell's vast internal membrane transport system, the Golgi apparatus (GA).

Results identified at least two enzymes involved in PSY1 glycosylation – H+-coupled amino acid transporter, HPAT1 -3 and, extremely likely to be a part of the process, RRA3. Free flow electrophoresis was applied to determine the protein modifications to extensins in the GA. Data collected implies that efficient arabinosylation of peptide hormones could be achieved in vitro if the substrates were hydroxylated first.

Results also show that the lipid composition of the membranes in different compartments in the GA is likely to play a key role in the localisation of membrane-associated proteins. Free flow electrophoresis also indicated which subcompartments were the points of protein structural changes.

EXHOMO has successfully identified many of the knowledge gaps in biochemical cascades for in-vitro production of two important phytohormones. The work has obvious applications in agriculture and plant breeding to fulfil a growing need for increased crop production.