Department of Plant Biology, Michigan State University, East Lansing, Michigan, USA.
Cell and Molecular Biology Program, Michigan State University, East Lansing, Michigan, USA.
Plant Physiol. 2022 Jun 1;189(2):906-921. doi: 10.1093/plphys/kiac052.
Nannochloropsis oceanica, like other stramenopile microalgae, is rich in long-chain polyunsaturated fatty acids (LC-PUFAs) such as eicosapentaenoic acid (EPA). We observed that fatty acid desaturases (FADs) involved in LC-PUFA biosynthesis were among the strongest blue light-induced genes in N. oceanica CCMP1779. Blue light was also necessary for maintaining LC-PUFA levels in CCMP1779 cells, and growth under red light led to a reduction in EPA content. Aureochromes are stramenopile-specific proteins that contain a light-oxygen-voltage (LOV)-sensing domain that associates with a flavin mononucleotide and is able to sense blue light. These proteins also contain a basic leucine zipper DNA-binding motif and can act as blue light-regulated transcription factors by associating with an E-box like motif, which we found enriched in the promoters of blue light-induced genes. We demonstrated that, in vitro, two CCMP1779 aureochromes were able to absorb blue light. Moreover, the loss or reduction of the expression of any of the three aureochrome genes led to a decrease in the blue light-specific induction of several FADs in CCMP1779. EPA content was also significantly reduced in NoAUREO2 and NoAUREO4 mutants. Taken together, our results indicate that aureochromes mediate blue light-dependent regulation of LC-PUFA content in N. oceanica CCMP1779 cells.
海洋盐藻与其他不等鞭毛藻类一样，富含长链多不饱和脂肪酸（LC-PUFAs），如二十碳五烯酸（EPA）。我们观察到，参与 LC-PUFA 生物合成的脂肪酸去饱和酶（FADs）是海洋盐藻 CCMP1779 中受蓝光诱导最强的基因之一。蓝光也是维持 CCMP1779 细胞 LC-PUFA 水平所必需的，而在红光下生长会导致 EPA 含量降低。Aureochromes 是不等鞭毛藻类特有的蛋白，含有一个光氧电压（LOV）感应结构域，与黄素单核苷酸结合，并能够感应蓝光。这些蛋白还含有碱性亮氨酸拉链 DNA 结合基序，通过与 E 盒样基序结合，它们可以作为蓝光调节的转录因子发挥作用，我们发现蓝光诱导基因的启动子中富含这种基序。我们证明，在体外，两种 CCMP1779 aureochromes 能够吸收蓝光。此外，任何一种 aureochrome 基因的缺失或表达减少都会导致 CCMP1779 中几种 FAD 的蓝光特异性诱导减少。EPA 含量在 NoAUREO2 和 NoAUREO4 突变体中也显著降低。总之，我们的结果表明，aureochromes 介导海洋盐藻 CCMP1779 细胞中 LC-PUFA 含量的蓝光依赖性调节。
