Doll, N. M. | bioRxiv Science

bioRxiv2019

A two-way molecular dialogue between embryo and endosperm required for seed development

The plant embryonic cuticle is a hydrophobic barrier deposited de novo by the embryo during seed development. At germination it protects the seedling from water loss and is thus critical for survival. Embryonic cuticle formation is controlled by a signaling pathway involving the protease ALE1 and the receptor-like kinases GSO1 and GSO2. We show that a sulfated peptide, TWISTED SEED1 (TWS1) acts as a GSO1/GSO2 ligand. Cuticle surveillance depends on the action of ALE1 which, unlike TWS1 and GSO1/2, is not produced in the embryo but in the neighboring endosperm. Cleavage of an embryo-derived TWS1 precursor by ALE1 releases the active peptide, triggering GSO1/2-dependent cuticle reinforcement in the embryo. A bidirectional molecular dialogue between embryo and endosperm thus safeguards cuticle integrity prior to germination.\n\nOne Sentence SummarySubtilase-mediated activation of the TWISTED SEED1 peptide provides spatial cues during embryo cuticle integrity monitoring.

plant biology↗

bioRxiv2019

Transcriptomics at maize embryo/endosperm interfaces identify a novel transcriptionally distinct endosperm sub-domain adjacent to the embryo scutellum (EAS)

Seeds are complex biological systems comprising three genetically distinct tissues nested one inside another (embryo, endosperm and maternal tissues). However, the complexity of the kernel makes it difficult to understand inter compartment interactions without access to spatially accurate information. Here we took advantage of the large size of the maize kernel to characterize genome-wide expression profiles of tissues at embryo/endosperm interfaces. Our analysis identifies specific transcriptomic signatures in two interface tissues compared to whole seed compartments: The scutellar aleurone layer (SAL), and the newly named endosperm adjacent to scutellum (EAS). The EAS, which appears around 9 days after pollination and persists for around 11 days, is confined to one to three endosperm cell layers adjacent to the embryonic scutellum. Its transcriptome is enriched in genes encoding transporters. The absence of the embryo in an embryo specific (emb) mutant can alter the expression pattern of EAS marker genes. The detection of cell death in some EAS cells together with an accumulation of crushed cell walls suggests that the EAS is a dynamic zone from which cell layers in contact with the embryo are regularly eliminated, and to which additional endosperm cells are recruited as the embryo grows.

plant biology↗