A strategy for interfering with the formation of thick cell walls in Haematococcus pluvialis by down-regulating the mannan synthesis pathway

The challenges associated with effective cell wall disruption remain an important bottleneck that has restricted efforts to extract astaxanthin from Haematococcus pluvialis. Here, available transcriptomic data and an Agrobacterium tumefaciens-mediated transformation system were used to establish an H. pluvialis strain in which the key cell wall formation-related enzyme α-1,6-mannosyltransferase (HpOCH1) was downregulated in an effort to thin cell walls and thereby simplify the astaxanthin extraction process. The cell wall remodeling activity observed in these HpOch1 knockdown H. pluvialis cells resulted in dramatic reductions in the mannan organization and protective ability of the established cell walls. The cell fragmentation rate increased by 58% in HpOch1- group relative to the control group. Critically, astaxanthin synthesis was not altered in the HpOch1 knockdown cells. Overall, this study highlights a novel technical approach to artificial cell wall thinning, offering a foundation for further efforts to more effectively leverage the astaxanthin resources of H. pluvialis.