Overexpression of a <i>MYB1</i> Transcription Factor Enhances Triacylglycerol and Starch Accumulation and Biomass Production in the Green Microalga <i>Chlamydomonas reinhardtii</i>

Abstract

Microalgae are promising platforms for biofuel production. Transcription factors (TFs) are emerging as key regulators of lipid metabolism for biofuel production in microalgae. We previously identified a novel TF MYB1, which mediates lipid accumulation in the green microalga <i>Chlamydomonas</i> under nitrogen depletion. However, the function of <i>MYB1</i> on lipid metabolism in microalgae under standard growth conditions remains poorly understood. Here, we examined the effects of <i>MYB1</i> overexpression (<i>MYB1-</i>OE) on lipid metabolism and physiological changes in <i>Chlamydomonas</i>. Under standard growth conditions, <i>MYB1-</i>OE transformants accumulated 1.9 to 3.2-fold more triacylglycerols (TAGs) than that in the parental line (PL), and total fatty acids (FAs) also significantly increased. Moreover, saturated FA (C16:0) was enriched in TAGs and total FAs in <i>MYB1-</i>OE transformants. Notably, starch and protein content and biomass production also significantly increased in <i>MYB1-</i>OE transformants compared with that in PL. Furthermore, RT-qPCR results showed that the expressions of key genes involved in TAG, FA, and starch biosynthesis were upregulated. In addition, <i>MYB1-</i>OE transformants showed higher biomass production without a compromised cell growth rate and photosynthetic activity. Overall, our results indicate that <i>MYB1</i> overexpression not only enhanced lipid content but also improved starch and protein content and biomass production under standard growth conditions. TF MYB1 engineering is a promising genetic engineering tool for biofuel production in microalgae.