Physiological, chemical and molecular characterisation of sugar alcohol accumulation in Leguminosae

Abstract

Sugar alcohols accumulate across a broad range of plant genera, often to concentrations exceeding that of soluble carbohydrates. While there is a general consensus on the function of sugar alcohols based on their physiochemical properties, gaps remain in understanding conditions that elicit sugar alcohol accumulation and its molecular control. Through a series of chemical, molecular, and physiological techniques, this thesis investigates the complexity of D-pinitol accumulation within the Leguminosae system and the transcriptional responses of key genes governing D-pinitol biosynthesis. In addition, naturally occurring compound specific carbon isotope abundances are used to evaluate the influence of D-pinitol synthesis on modelling water use efficiency. Assessing the chemical composition of the soluble leaf fraction found that DPinitol significantly increased over development in both chickpea (Cicer arietinum) grown in field and in soybean (Glycine max) grown under controlled environmental conditions. Compound specific carbon isotope abundance (δ13C) in samples collected from chickpea grown in field and soybean grown under elevated atmospheric CO2 established that concentrations of D-pinitol in the soluble fraction coupled with high Δ13C of the D-pinitol pool imparts a substantial influence over predictions of water use efficiency modelled from the leaf soluble fraction. Quantitative molecular investigations found that the inositol-1-phosphate synthase (INPS) gene is transcriptionally up regulated in response to a gradual water deficit in soybean grown in controlled conditions. While future studies must consider a wider range of legume species and genotypes when investigating sugar alcohol biosynthesis, the studies presented here suggest that the accumulation of D-pinitol in legumes is a good candidate for the improvement of plant performance and resilience.