Evolutionary lineages and functional diversification of plant hexokinases

Area of Science:

• Plant molecular biology
• Biochemistry
• Evolutionary biology

Background:

• Plant hexokinase (HXK) gene families vary in size (5-11 genes) across species.
• HXK proteins exhibit diverse functions, acting as metabolic catalysts, glucose signaling molecules, or non-catalytic regulatory homologs.

Purpose of the Study:

• To develop a predictive method for assigning functions to HXK proteins within species.
• To investigate the presence of HXK-dependent glucose signaling proteins in both primitive and advanced (angiosperm) plants.

Main Methods:

• Molecular phylogeny analysis.
• Experimental testing including protoplast transient expression assays.
• Comparative genomics across 10 plant species.

Main Results:

• Non-catalytic HXK homologs are found in all studied plants, including primitive species like Selaginella moellendorffi.
• Angiosperm HXKs show conserved catalytic activity and subcellular targeting, with most localized to mitochondria, some to plastids, and others to the cytosol.
• HXK glucose signaling proteins are likely present in all higher plants and S. moellendorffi.

Conclusions:

• HXK-mediated glucose signaling is a conserved and widespread process in plants, from primitive to angiosperm lineages.
• The utilization of glucose by plant HXK isoforms for metabolism and/or regulation is a fundamental and conserved biological process.