Nitrogen assimilation in high lipid (triacylglycerol) transgenic Arabidopsis

This study aimed to gain a greater understanding of the reason(s) for growth limitation in high lipid Arabidopsis thaliana line ‘D1o3-3#47’ under nitrate (NO₃⁻) nutrition, as reported by the Plant Biotechnology group at Agresearch, Palmerston North. Growth (dry weight, DW) and nitrogen (N) related measurements were carried out for D1o3-3#47 and wild type (WT) Arabidopsis plants, initially under a range and then under a selected NO₃⁻ concentration. The study also investigated whether the vegetative growth in any way correlates with the leaf fatty acid content of the Arabidopsis lines studied. Finally, the growth of D1o3-3#47 plants was compared to WT plants initially under a range and then under a selected concentration of four N forms: NO₃⁻, ammonium (NH₄⁺), urea and glutamine. D1o3-3#47 plants showed only 50% of the growth of WT plants at higher (≥ 2 mM) NO₃⁻-N concentrations. Under NO₃⁻ nutrition, D1o3-3#47 plants showed either similar or occasionally greater shoot N% (of g DW), but consistently less shoot total-N than WT plants. Shoot NO₃⁻-N, leaf soluble protein content and leaf nitrate reductase activity (NRA) were greater in D1o3-3#47 plants than WT plants. A weak negative correlation was found between growth and leaf fatty acid content of the Arabidopsis lines studied. D1o3-3#47 plants showed between 53-59% of the growth of WT plants under selected N concentration of NO₃⁻, ammonium (NH₄⁺), urea and glutamine, and their growth was not better than WT plants even under Thrive® nutrition. It appears that D1o3-3#47 plants show limited growth regardless of the N availability or form. Based on these results the possible reasons for the limited growth of D1o3-3#47 plants as compared to WT plants were discussed.