Glycosylceramide assembly and function in a model bryophyte
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Research Conducted
To elucidate the functions of glycosylceramides, we generated and characterized mutants deficient in multiple steps contributing to their assembly in the model moss Physcomitrium patens . We mutagenized SPHINGOLIPID Δ8-DESATURASE , whose products are preferentially incorporated into glycosylceramides, and a suite of higher-order mutants combining sphingolipid Δ4-desaturase and glycosyl ceramide synthase .
Methods
We used targeted lipidomics to describe the chemotypes of all mutants. We used quantitative phenotype analysis, transcriptomics, and phytohormone profiling to understand the effects of these chemotypes on development and physiology.
Key Results
These mutants present a range of phenotypes that collectively indicate that in P. patens (1) glycosylceramide deficiency impairs development, largely due to imbalance in free ceramide homeostasis (2) the synthesis of glycosylceramides is dependent upon the presence of a specific free ceramide profile (3) the Δ4-, but not the Δ8-desaturation, is strictly required for glycosylceramide synthesis, (4) cell division and differentiation, but not cell expansion, are affected by sphingolipid imbalance, and (5) sphingolipid imbalance results in oxylipin accumulation.
Conclusion
Collectively, our results elucidate the assembly and functions of glycosylceramides in a model bryophyte, and highlight conserved and specialized aspects of sphingolipid metabolism among plants.
