BnaNTT2 regulates ATP homeostasis in plastid to sustain lipid metabolism and plant growth in Brassica napus

Lipidomic and Metabolomic Analyses Reveal Changes of Lipid and Metabolite Profiles in Rapeseed during Nitrogen Deficiency

Nitrogen is one of the most essential macronutrients for plant growth and its availability in soil is vital for agricultural sustainability and productivity. However, excessive nitrogen application could reduce the nitrogen use efficiency and produce environmental pollution. Here, we systematically determined the response in lipidome and metabolome in rapeseed during nitrogen starvation. Plant growth was severely retarded during nitrogen deficiency, while the levels of most amino acids were significantly decreased. The level of monogalactosyldiacyglycerol (MGDG) in leaves and roots was significantly decreased, while the level of digalactosyldiacylglycerol (DGDG) was significantly decreased in roots, resulting in a significant reduction of the MGDG/DGDG ratio during nitrogen starvation. Meanwhile, the levels of sulfoquinovosyl diacylglycerol, phosphatidylglycerol and glucuronosyl diacylglycerol were reduced to varying extents. Moreover, the levels of metabolites in the tricarboxylic acid cycle, Calvin cycle and energy metabolism were changed during nitrogen deficiency. These findings show that nitrogen deprivation alters the membrane lipid metabolism and carbon metabolism, and our study provides valuable information to further understand the response of rapeseed to nitrogen deficiency at the metabolism level.

Progress in understanding and improving oil content and quality in seeds

The world's population is projected to increase by two billion by 2050, resulting in food and energy insecurity. Oilseed crops have been identified as key to address these challenges: they produce and store lipids in the seeds as triacylglycerols that can serve as a source of food/feed, renewable fuels, and other industrially-relevant chemicals. Therefore, improving seed oil content and composition has generated immense interest. Research efforts aiming to unravel the regulatory pathways involved in fatty acid synthesis and to identify targets for metabolic engineering have made tremendous progress. This review provides a summary of the current knowledge of oil metabolism and discusses how photochemical activity and unconventional pathways can contribute to high carbon conversion efficiency in seeds. It also highlights the importance of ¹³C-metabolic flux analysis as a tool to gain insights on the pathways that regulate oil biosynthesis in seeds. Finally, a list of key genes and regulators that have been recently targeted to enhance seed oil production are reviewed and additional possible targets in the metabolic pathways are proposed to achieve desirable oil content and quality.

Fatty acid exporter 1 enhances seed oil content in Brassica napus

Fatty acid exporter 1 (FAX1) is an initial transporter for fatty acid (FA), in charge of transporting FA from the inside of the plastid to the outside. Brassica napus (B. napus) has nineteen members in the FAX family, of which there are six FAX1 homologous genes. Here, we generated the BnaFAX1 CRISPR mutants (BnaA09.FAX1 and BnaC08.FAX1 were both edited) and overexpression (OE) plants of BnaA09.FAX1 in B. napus. The results showed that the FA content was increased by 0.6-0.9% in OE plant leaves, and the seed oil content was increased by 1.4-1.7% in OE lines, compared to WT. Meanwhile, the content of triacylglycerol, diacylglycerol, and phosphatidylcholine was significantly increased in OE seeds. Moreover, seedling biomass and plant height of OE plants were increased compared to WT plants. However, the traits above had no significant difference between the mutants and WT. These results suggest that BnaA09.FAX1 plays a role in improving seed oil accumulation and plant growth, while the function of BnaFAX1 may be compensated by other homologous genes of BnaFAX1 and other BnaFAX genes in the mutants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-022-01346-0.