RTG 1962 – Guest Talk: Sphingolipid desaturation in Arabidopsis thaliana and Physcomitrella patens evolved independently

Jul 16
16. Juli 2019 17:00 Uhr bis 18:00 Uhr
Prof. Dr. Ivo Feussner, Göttingen | Seminar Room Cell Biology (00.581), Staudtstraße

Invitation to RTG 1962 – Guest Talk
“Sphingolipid desaturation in Arabidopsis thaliana and Physcomitrella
patens evolved independently”

Prof. Dr. Ivo Feussner, Georg-August-University Göttingen

In plants, adaptation to low temperature is a central mechanism for survival. It involves the modification of lipids to maintain membrane fluidity. We established the lipid profile of P. patens that allowed us to identify the function of a novel cold-induced desaturase, named SPHINGOLIPID FATTY ACID DESATURASE (PpSFD) by comparing the profile of three sfd loss-of-function mutants with the one of the wild type (WT) cultures. PpSFD catalyzes the formation of double bonds into C24 and C26 fatty acids (FA), which are present in sphingolipids and some phospholipid classes. The introduction of the double bond occurs at the n-8 position in C24 FA. Furthermore, P. patens modifies its overall lipid composition at low temperatures by accumulating neutral lipids and sphingolipids,
while simultaneously adjusting the FA of glycolipids to contain more very-long-chain poly-unsaturated FA (VLCPUFA) and those of phospholipids to contain less VLC-PUFA. By contrast, vascular plants like Arabidopsis thaliana
increase the amount of PUFA in all lipid classes in the cold. In sfd mutants, overall levels of neutral lipids are elevated and sterols are reduced. However, FA adjustment in glycolipids and phospholipids upon cold stress does not occur
any more, which suggests that the mutants have either a defect in cold perception or in executing a response against cold. Plate cultures of Ppsfd mutants grown at long-term cold stress show reduced tissue growth and contain less chlorophyll than the WT. This cold stress phenotype is similar to the Atads2.1 (ACYL-COENZYME A DESATURASELIKE 2) mutant from A. thaliana. Heterologous expression of PpSFD in the Atads2.1 mutant resulted in the recovery
of the cold-sensitive phenotype. While the levels of unsaturated C24 FA were similar as in WT, the double-bond position was similar to P. patens WT. Because AtADS2 is a methyl-end desaturase whereas PpSFD is a cytochrome-b5
fusion desaturase, we suggest that PpSFD and AtADS2 evolved independently during evolution going back at least to the split of vascular and non-vascular plants. PpSFD is therefore the first described cytochrome-b5 fusion desaturase
with a substrate specificity towards VLC-FA found in sphingolipids and with the discovered n-8 positional preference.

Guests are welcome!
gez. Prof. Dr. R. Böckmann

Tuesday, 16th July 2019 at 17.00 (s.t.)
Venue: Department Biology, Seminar Room Cell Biology (00.581),
Building B1, Floor 00, Staudtstraße 5, 91058 Erlangen