Symplastic domains in the Arabidopsis shoot apical meristem correlate with PDLP1 expression patterns

Abstract

Symplastic domains in plants are defined by spatial limitations on cell-to-cell communication through plasmodesmata (Pds) and establish tissue boundaries necessary for metabolic and developmental programming. With the exception of the physical closure of Pds by callose, the cues and the processes for creating symplastic domains remain poorly understood. Recently, we identified a novel family of eight proteins, called Pd-located protein 1 (PDLP1). These proteins span the plasma membrane within Pds and likely form part of a signal transduction system that perceives external signals to regulate molecular trafficking between cells. For two members of this family that have high expression in the shoot apex we show that they have defined and partially overlapping tissue-specific expression patterns that correlate in part with previously defined symplastic domains. The importance of non-cell-autonomous proteins in shoot development and of the spatial rules that govern leaf and floral development highlight the need to have a clearer understanding of symplastic domains.

Keywords: Arabidopsis; functional redundancy; plasmodesmata; plasmodesmata-located protein 1; shoot apical meristem; symplastic domains.

Figure 1

Plant-wide tissue expression profiles for the PDLP1 family. (A) Heat-map representation of the public expression data (www.genevestigator.ethz.ch) for the Arabidopsis PDLP1 gene family. High expression in the shoot apex was seen for At2g33330 and At1g04520 (red boxes). (B) Tissues sources tabulated in (A).

Figure 2

Expression pattern of two members of the PDLP1 plasmodemal protein family at the inflorecence shoot apical meristem of Arabidopsis. (A and C) At2g33330:GFP. (B and D) At1g04520:GFP. (A and B) GFP fluorescence seen from the top view of Arabidopsis inflorescence meristems (maximum projection of transverse confocal scans). (C and D) GFP fluorescence in longitudinal confocal sections through Arabidopsis inflorescence meristems. White star indicates central zone position. Grey arrows indicate the boundary between floral primordia (P; P1–P7) and the meristem. Bars = 20 µm.