Exploring the key genes of fucoxanthin biosynthesis in Phaeodactylum tricornutum under phosphorus deficiency, red light and yellow light using WGCNA.

Abstract

Weighted gene co-expression network analysis (WGCNA) is a method for analysing gene expression patterns across multiple samples, clustering genes with similar expression patterns and identifying key genes associated with specific traits or phenotypes. In this study, we investigated the effects of fucoxanthin accumulation in Phaeodactylum tricornutum in response to abiotic stresses of phosphorus deficiency, red light, and yellow light using transcriptome sequencing and weighted gene co-expression network analysis. The results showed that compared to the control, the fucoxanthin content of P. tricornutum was significantly increased after phosphorus deficiency and red light treatment (P<0.05), but significantly decreased after yellow light treatment (P<0.05). A weighted gene co-expression network was constructed using 10,392 genes obtained from transcriptome sequencing, and β=18 (R2>0.8) was chosen as a soft threshold in order to ensure a scale-free network. A total of 10 co-expression modules were identified by correlation analysis of fucoxanthin content, with the purple module positively correlated with fucoxanthin content (r=0.9, P=1E-200), and 9 key genes were identified, including five genes in the fucoxanthin biosynthesis pathway (DXR, PSY, PDS1, ZEP2, VDL2) and 4 transcription factors (bHLH5, HOX2, CCHH13, HSF1b). Further qRT-PCR confirmed that key genes were more highly expressed in the phosphorus deficiency treatment and linear regression analysis showed that the relative gene expressions were all highly correlated with the transcriptome data. The results of this study provide a basis for further investigation of the complex regulatory mechanisms of fucoxanthin in P. tricornutum.