Chongqing Key Laboratory of Plant Resource Conservation and Germplasm Innovation, School of Life Sciences, Southwest University, Chongqing 400715, China.
Research Center of Bioremediation and Bioenergy, College of Resources and Environment, Southwest University, Beibei, Chongqing 400715, China.
Plant Physiol. 2020 Apr;182(4):1910-1919. doi: 10.1104/pp.19.01344. Epub 2020 Feb 4.
Triacylglycerols (TAGs) are the major storage form of seed oil in oilseed plants. They are biosynthesized de novo in seed plastids and then transported into the endoplasmic reticulum. However, the transport mechanism for plastid fatty acids in developing seeds remains unknown. Here, we isolated two novel plastid fatty acid exporters (FATTYACID EXPORT 2 [FAX2] and FAX4, respectively) specifically abundant in seed embryos during the seed-filling stage in Arabidopsis (). FAX2 and FAX4 were both localized to the chloroplast membrane. and loss-of-function mutations caused deficiencies in embryo and cotyledon development. Seeds of double mutants exhibited significantly reduced TAG contents but elevated levels of plastid lipid contents compared with those of wild-type plants. By contrast, overexpression of or enhanced TAG deposition. Seed-feeding experiments showed that the two FAX proteins transported C-plastid fatty acids and C-oleic acids for TAG biosynthesis during the seed-filling stage. Together, our data demonstrate that FAX2 and FAX4 play critical roles in transporting plastid fatty acids for TAG biosynthesis during seed embryo development. These two transporters may have broad application for increasing oil yield in oilseed crops.
TAGs 是油料植物种子油的主要储存形式。它们在种子质体中从头合成，然后被运输到内质网。然而，在发育中的种子中，质体脂肪酸的运输机制尚不清楚。在这里，我们分别分离了两个在拟南芥种子灌浆期种子胚胎中特异丰富的新型质体脂肪酸输出蛋白（FAX2 和 FAX4）。FAX2 和 FAX4 均定位于叶绿体膜上。fax2 和 fax4 的功能缺失突变导致胚胎和子叶发育缺陷。fax2fax4 双突变体种子的 TAG 含量显著降低，但与野生型植物相比，质体脂质含量升高。相比之下，过表达 或 增强了 TAG 的沉积。种子喂养实验表明，这两种 FAX 蛋白在种子灌浆期运输 C-质体脂肪酸和 C-油酸以进行 TAG 生物合成。总之，我们的数据表明 FAX2 和 FAX4 在种子胚胎发育过程中质体脂肪酸向 TAG 生物合成的运输中发挥关键作用。这两种转运蛋白可能在提高油料作物的产油量方面具有广泛的应用。
