The trade-off between protein and oil storage in oilseed crops has been tested here in oilseed rape (Brassica napus) by analyzing the effect of suppressing key genes encoding protein storage products (napin, cruciferin). The phenotypic outcomes were assessed using nuclear magnetic resonance and mass spectrometry imaging, microscopy, transcriptomics, proteomics, metabolomics, lipidomics, immunological assays as well as by flux balance analysis. Surprisingly, the profile of storage products was only moderately changed in RNAi transgenics. However, embryonic cells had undergone remarkable architectural rearrangements. The suppression of storage proteins led to the elaboration of membrane stacks enriched with oleosin (6-fold higher protein abundance) and novel ER morphology. Protein rebalancing, and amino acid metabolism were focal points of the metabolic adjustments to maintain embryonic carbon/nitrogen homeostasis. Flux balance analysis indicated a rather minor additional demand for cofactors (ATP, NADPH). The conclusion was that cellular plasticity in seeds protects against perturbations to its storage capabilities, and hence contributes materially to homeostasis. The study provides novel mechanistic insights into the intriguing link between lipid and protein storage, which have implications for biotechnological strategies directed at the improvement of oilseed crops.

Proteomics, metabolomics, RNA-sequencing, Magnetic resonance imaging, MALDI