Plasmodesmata formation and cell-to-cell transport are reduced in decreased size exclusion limit 1 during embryogenesis in Arabidopsis

Abstract

In plants, plasmodesmata (PD) serve as channels for micromolecular and macromolecular cell-to-cell transport. Based on structure, PD in immature tissues are classified into two types, simple and branched (X-and Y-shaped) or twinned. The maximum size of molecules capable of PD transport defines PD aperture, known as the PD size exclusion limit. Here we report an Arabidopsis mutation, decreased size exclusion limit1 (dse1), that exhibits reduced cell-to-cell transport of the small (524 Da) fluorescent tracer 8-hydroxypyrene-1,3,6-trisulfonic acid at the midtorpedo stage of embryogenesis. Correspondingly, the fraction of X-and Y-shaped and twinned PD was reduced in dse1 embryos compared with WT embryos at this stage, suggesting that the frequency of PD is related to transport capability. dse1 is caused by a point mutation in At4g29860 (previously termed TANMEI) at the last donor splice site of its transcript, resulting in alternative splicing in both the first intron and the last intron. AtDSE1 is a conserved eukaryotic 386-aa WD-repeat protein critical for Arabidopsis morphogenesis and reproduction. Similar to its homologs in mouse, null mutants are embryo-lethal. The weak loss-of-function mutant dse1 exhibits pleiotropic phenotypes, including retarded vegetative growth, delayed flowering time, dysfunctional male and female organs, and delayed senescence. Finally, silencing of DSE1 in Nicotiana benthamiana leaves leads to reduced movement of GFP fused to tobacco mosaic virus movement protein. Thus, DSE1 is important for regulating PD transport between plant cells.

Does Don Fisher's high-pressure manifold model account for phloem transport and resource partitioning?

“…Plasmodesmal densities are under both positional and developmental control (Burch-Smith and Zambryski, 2012). Regulatory mechanisms controlling plasmodesmal densities are beginning to be discovered and these exert a predictable positive influence on overall symplasmic conductance (e.g., Burch-Smith and Zambryski, 2010; Xu et al, 2012). For root apices, plasmodesmal densities in transverse walls are higher than those in periclinal walls and both densities progressively decrease with distance from the vascular tissues (Zhu et al, 1998).…”

Plasmodesmata dynamics are coordinated by intracellular signaling pathways

“…The first looked for altered movement of fluorescent tracers in embryo-defective mutants, reasoning that any mutant with strong effects on PD transport would exhibit severely disrupted development [3]. From this screen, three mutants have been characterized so far: increased size exclusion limit 1 and 2 ( ise1 and ise2 ), which have increased PD transport, and decreased size exclusion limit 1 ( dse1 ), which has decreased PD transport [3,7–10]. Two other screens searched for mutants with decreased protein movement (i) from the phloem to surrounding tissues or (ii) from the mesophyll to the epidermis.…”

Specific Membrane Lipid Composition Is Important for Plasmodesmata Function in Arabidopsis

“…PD span the thick cell wall of virtually all plant cells, establishing both cytoplasmic and membrane continuity throughout the entire plant body. In recent years, PD have emerged as key elements of the cell-to-cell communication machinery and, as such, have been implicated in processes guaranteeing the collaborative functioning of the cells, the cooperative responses to exogenous and endogenous stimuli, and controlled developmental events (Chitwood and Timmermans, 2010;Dunoyer et al, 2010;Vatén et al, 2011;Xu et al, 2011Xu et al, , 2012Burch-Smith and Zambryski, 2012;Furuta et al, 2012;Koizumi et al, 2012;Maule et al, 2012;Wu and Gallagher, 2012;Faulkner et al, 2013;Stahl et al, 2013;Tilsner et al, 2013;Wang et al, 2013;Han et al, 2014;Vaddepalli et al, 2014).…”