Identification of symplasmic domains in the embryo and seed of Sedum acre L. (Crassulaceae)

Abstract

Main conclusion Our study demonstrated that symplasmic communication between Sedum acre seed compartments and the embryo proper is not uniform. The presence of plasmodesmata (PD) constitutes the structural basis for information exchange between cells, and symplasmic communication is involved in the regulation of cell differentiation and plant development. Most recent studies concerning an analysis of symplasmic communication between seed compartments and the embryo have been predominantly performed on Arabidopsis thaliana. The results presented in this paper describe the analysis of symplasmic communication on the example of Sedum acre seeds, because the ultrastructure of the seed compartments and the embryo proper, including the PD, have already been described, and this species represents an embryonic type of development different to Arabidopsis. Moreover, in this species, an unusual electron-dense dome associated with plasmodesmata on the border between the basal cell/chalazal suspensor cells and the basal cell/the endosperm has been described. This prompted the question as to whether these plasmodesmata are functional. Thus, the aim of this study was to describe the movement of symplasmic transport fluorochromes between different Sedum seed compartments, with particular emphasis on the movement between the basal cell and the embryo proper and endosperm, to answer the following questions: (1) are seeds divided into symplasmic domains; (2) if so, are they stable or do they change with the development? The results have shown that symplasmic tracers movement: (a) from the external integument to internal integument is restricted; (b) from the basal cell to the other part of the embryo proper and from the basal cell to the endosperm is also restricted; (c) the embryo is a single symplasmic domain with respect to molecules of a molecular weight below 0.5 kDa.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-016-2619-y) contains supplementary material, which is available to authorized users.

Development of Embryo Suspensors for Five Genera of Crassulaceae with Special Emphasis on Plasmodesmata Distribution and Ultrastructure

“…PD between suspensor and endosperm are found only in a few species (mainly among Sedum genus; e.g., [26]) assuming that symplasmic exchanges may occur but substantially stop early in seed development. On the contrary, our findings confirm the previously evidenced in Sedum [26,30] symplasmic connections of the suspensor cells both with the endosperm and the embryo proper cells (e.g., Figure 9A,B). Interestingly, the symplasmic communication exists till the end of embryogenesis and suspensor degradation.…”

“…Recent studies on Sedum acre in Crassulaceae have analyzed symplasmic communication between the basal cell and the embryo proper and endosperm. These studies showed that symplasmic communication is nonuniform [30]. Indeed, despite many important studies about the embryogenesis of Crassulaceae, there is a lack of a detailed description of ultrastructural aspects for a large number of genera from this family.…”

Ultrastructural and cytochemical aspects of female gametophyte development in Sedum hispanicum L. (Crassulaceae)

“…Experiments conducted on S. acre revealed that the discovered plasmodesmata are functional, but only in directions of the basal cell-embryo proper and basal cell endosperm. Movement of symplasmic transport fluorochromes in the opposite direction was not detected, so probably they are limited (Wróbel-Marek et al 2017 ). Unidirectional movement through plasmodesmata was not fully confirmed, but data revealed such a possibility (Wróbel-Marek et al 2017 ).…”

“…Movement of symplasmic transport fluorochromes in the opposite direction was not detected, so probably they are limited (Wróbel-Marek et al 2017 ). Unidirectional movement through plasmodesmata was not fully confirmed, but data revealed such a possibility (Wróbel-Marek et al 2017 ). Possibly, during megasporogenesis, such plasmodesmata regulated the flow of the nutritional substances, but this is only a hypothesis.…”

Seed Transmission of Tobamoviruses: Aspects of Global Disease Distribution

“…The funiculus phloem reaches a phloem-unloading domain at the chalazal area of the outer integument, which either alone or together with the inner integument evolves to the seed coat, which differs between seed species as well. Using fluorescent probes, it has been shown that the entire outer integument at the end of the vascular bundle sheath of the funiculus is an extended symplasmic domain in Arabidopsis thaliana [99], and in Crassulaceae seeds [100], the inner integument and the embryo are separated symplasmic domains. In legumes,…”