Abstract
The plasmodesmata (PD) regulates the passage of biomolecules between neighboring cells. The primary PD refers to single-stranded, linear entities that are created during cytokinesis, whereas the secondary PD (2˚-PD) have branches or higher-order architectures that are transformed from the primary PD after cytokinesis. The 2˚-PD occurs in the cell wall of the companion cell (CC)-sieve element (SE) in source leaves, regulating sucrose passage into SE. To date, the molecular mechanism of 2˚-PD formation is little understood. We recently isolated restricted sucrose export1 mutants the showed enhanced sugar accumulation and freezing tolerance in the source leaves of Arabidopsis thaliana. rsx1 mutants showed nascent 2˚-PD that is arrested in the middle lamellar of the cell wall between CC and SE. RSX1 encodes a pectate lyase, which hydrolyzes low-esterified pectin. Because pectin forms middle lamellar in the cell wall, we propose that RSX1 assists 2˚-PD formation by punctuating the pectin middle lamellar.
