Department of Botany and Plant Biology, University of Geneva, Geneva, Switzerland.
Department of Plant Molecular Biology, University of Lausanne, Lausanne, Switzerland.
Dev Cell. 2021 Nov 22;56(22):3066-3081.e5. doi: 10.1016/j.devcel.2021.10.005. Epub 2021 Oct 26.
In Arabidopsis mature seeds, the onset of the embryo-to-seedling transition is nonautonomously controlled, being blocked by endospermic abscisic acid (ABA) release under unfavorable conditions. Whether the mature endosperm governs additional nonautonomous developmental processes during this transition is unknown. Mature embryos have a more permeable cuticle than seedlings, consistent with their endospermic ABA uptake capability. Seedlings acquire their well-sealing cuticles adapted to aerial lifestyle during germination. Endosperm removal prevents seedling cuticle formation, and seed reconstitution by endosperm grafting onto embryos shows that the endosperm promotes seedling cuticle development. Grafting different endosperm and embryo mutant combinations, together with biochemical, microscopy, and mass spectrometry approaches, reveal that the release of tyrosylprotein sulfotransferase (TPST)-sulfated CIF2 and PSY1 peptides from the endosperm promotes seedling cuticle development. Endosperm-deprived embryos produced nonviable seedlings bearing numerous developmental defects, not related to embryo malnutrition, all restored by exogenously provided endosperm. Hence, seedling establishment is nonautonomous, requiring the mature endosperm.
在拟南芥成熟种子中，胚胎到幼苗的转变起始是非自主控制的，在不利条件下，通过胚乳释放脱落酸（ABA）来阻断。在这个转变过程中，成熟胚乳是否控制其他非自主发育过程尚不清楚。成熟的胚胎比幼苗具有更具渗透性的角质层，这与其胚乳吸收 ABA 的能力一致。幼苗在萌发过程中获得了适应气生生活的良好密封角质层。胚乳去除阻止了幼苗角质层的形成，而通过胚乳嫁接到胚胎上进行的种子再构成表明胚乳促进了幼苗角质层的发育。通过嫁接不同的胚乳和胚胎突变体组合，以及生化、显微镜和质谱方法，揭示了从胚乳中释放酪氨酸蛋白硫基转移酶（TPST）-硫酸化 CIF2 和 PSY1 肽，促进了幼苗角质层的发育。缺乏胚乳的胚胎产生了许多与胚胎营养不良无关的、无法存活的幼苗缺陷，所有这些缺陷都可以通过外源提供的胚乳来恢复。因此，幼苗的建立是非自主的，需要成熟的胚乳。
