Golgi fucosyltransferase coordinates the energy reallocation and laminaran accumulation in diatom Phaeodactylum tricornutum

Fucosyltransferase (FucT), catalyzed the N-glycan structure modification of glycoprotein, played critical roles in cell development and stress resistance. However, little was known about the function of PtFucT in the regulation of energy partition and important metabolites, especially in a widespread model diatom Phaeodactylum tricornutum. In this study, the knock-out mutant of PtFucT1 was analyzed comprehensively from physiological, transcriptional, and N-glycoprotein levels. The cell proliferation and photosynthesis of PtFucT1 mutant was significantly inhibited, while the accumulation of laminaran and TAG content was activated, implying the energy reallocation in cell. The upregulation of laminaran biosynthesis and downregulation of its degradation metabolism further demonstrated the increase of laminaran content from transcription level. Moreover, the PGM was downregulated in transcription level and N-glycoprotein abundance while PGM/UGP protein complex was upregulated, hinting that glucose-6-phosphate was preferred to synthesize the UDP-glucose and laminaran directly in an energy-efficient strategy. At the same time, the activation of the ERQC system, and restrain of the ERAD mechanism implied the regulating capacity in protein correction and degradation. Our results provided new insights into the function of PtFucT1 in the energy allocation and the energy-efficient strategy of laminaran. It would help comprehensively clarify the function of PtFucT and develop diatoms as microbial cell factories to efficient synthesize laminaran.