Department of Plant Molecular Biology, University of Lausanne, Lausanne CH-1015, Switzerland.
Electron Microscopy Facility, University of Lausanne, Lausanne CH-1015, Switzerland.
Proc Natl Acad Sci U S A. 2024 May 21;121(21):e2314570121. doi: 10.1073/pnas.2314570121. Epub 2024 May 13.
Lipid polymers such as cutin and suberin strengthen the diffusion barrier properties of the cell wall in specific cell types and are essential for water relations, mineral nutrition, and stress protection in plants. Land plant-specific glycerol-3-phosphate acyltransferases (GPATs) of different clades are central players in cutin and suberin monomer biosynthesis. Here, we show that the // clade in , which is known to mediate cutin formation, is also required for developmentally regulated root suberization, in addition to the established roles of in suberization. The / clade is mainly required for abscisic acid-regulated suberization. In addition, the / clade is crucial for the formation of the typical lamellated suberin ultrastructure observed by transmission electron microscopy, as distinct amorphous globular polyester structures were deposited in the apoplast of the double mutant, in contrast to the thinner but still lamellated suberin deposition in the triple mutant. Site-directed mutagenesis revealed that the intrinsic phosphatase activity of GPAT4, GPAT6, and GPAT8, which leads to monoacylglycerol biosynthesis, contributes to suberin formation. GPAT5/7 lack an active phosphatase domain and the amorphous globular polyester structure observed in the double mutant was partially reverted by treatment with a phosphatase inhibitor or the expression of phosphatase-dead variants of // Thus, GPATs that lack an active phosphatase domain synthetize lysophosphatidic acids that might play a role in the formation of the lamellated structure of suberin. GPATs with active and nonactive phosphatase domains appear to have nonredundant functions and must cooperate to achieve the efficient biosynthesis of correctly structured suberin.
脂质聚合物，如角质和栓质，增强了细胞壁在特定细胞类型中的扩散屏障特性，对于植物的水分关系、矿物质营养和应激保护至关重要。不同进化枝的陆生植物特异甘油-3-磷酸酰基转移酶（GPAT）是角质和栓质单体生物合成的核心。在这里，我们表明，已知介导角质形成的 // 进化枝，除了在栓质形成中的既定作用外，对于发育调节的根栓质化也是必需的。/ 进化枝主要需要脱落酸调节的栓质化。此外，/ 进化枝对于透射电子显微镜观察到的典型层状栓质超微结构的形成至关重要，因为与 // 三重突变体中较薄但仍呈层状的栓质沉积相比，在 // 双突变体的质外体中沉积了独特的无定形球形聚酯结构。定点突变揭示了 GPAT4、GPAT6 和 GPAT8 的内在磷酸酶活性导致单酰基甘油的生物合成，有助于栓质的形成。GPAT5/7 缺乏活性磷酸酶结构域，并且在 // 双突变体中观察到的无定形球形聚酯结构部分通过用磷酸酶抑制剂处理或表达 // 的磷酸酶失活变体而被逆转。因此，缺乏活性磷酸酶结构域的 GPAT 合成溶血磷脂酸，可能在栓质的层状结构形成中发挥作用。具有活性和非活性磷酸酶结构域的 GPAT 似乎具有非冗余功能，并且必须合作以实现正确结构的栓质的有效生物合成。
