Lipid catabolism in germinating seeds provides energy and substrates for initial seedling growth, but how this process is regulated is not well understood. Here, we show that an AT-hook motif-containing nuclear localized (AHL) protein regulates lipid mobilization and fatty acid β-oxidation during seed germination and seedling establishment. AHL4 was identified to directly interact with the lipid mediator phosphatidic acid (PA). Knockout (KO) of AHL4 enhanced, but overexpression (OE) of AHL4 attenuated, triacylglycerol (TAG) degradation and seedling growth. Normal seedling growth of the OE lines was restored by sucrose supplementation to the growth medium. AHL4-OE seedlings displayed decreased expression of genes involved in TAG hydrolysis and fatty acid oxidation, whereas the opposite was observed in AHL4-KOs. These genes contained AHL4-binding cis elements, and AHL4 was shown to bind to the promoter regions of genes encoding the TAG lipases SDP1 and DALL5 and acyl-thioesterase KAT5. These AHL4–DNA interactions were suppressed by PA species that bound to AHL4. These results indicate that AHL4 suppresses lipid catabolism by repressing the expression of specific genes involved in TAG hydrolysis and fatty acid oxidation, and that PA relieves AHL4-mediated suppression and promotes TAG degradation. Thus, AHL4 and PA together regulate lipid degradation during seed germination and seedling establishment.

发芽种子中的脂质分解代谢为幼苗的初始生长提供了能量和底物，但是如何调节该过程尚不清楚。在这里，我们表明，包含AT钩基序的核定位（AHL）蛋白在种子发芽和幼苗建立过程中调节脂质动员和脂肪酸β-氧化。已确定AHL4与脂质介体磷脂酸（PA）直接相互作用。敲除（KO）的AHL4增强，但过表达（OE）AHL4衰减，三酰甘油（TAG）降解和幼苗生长。通过向生长培养基中添加蔗糖，可以恢复OE系的正常幼苗生长。AHL4-OE幼苗显示参与TAG水解和脂肪酸氧化的基因表达降低，而在AHL4- KOs中则相反。这些基因包含结合AHL4的顺式元件，并且显示AHL4与编码TAG脂肪酶SDP1和DALL5以及酰基硫酯酶KAT5的基因的启动子区域结合。这些AHL4–DNA相互作用被与AHL4结合的PA物种抑制。这些结果表明，AHL4通过抑制与TAG水解和脂肪酸氧化有关的特定基因的表达来抑制脂质分解代谢，而PA可以缓解AHL4介导的抑制并促进TAG降解。因此，AHL4和PA一起调节种子发芽和幼苗建立过程中的脂质降解。