Developing prolamine protein bodies are associated with the cortical cytoskeleton in rice endosperm cells

Abstract

The mRNAs that encode the prolamine storage proteins in rice (Oryza sativa L.) endosperm cells are enriched on the surface of the prolamine protein bodies (PBs), a subcellular structure consisting of a prolamine intracisternal granule surrounded by rough endoplasmic reticulum membrane. Previous biochemical studies (D.G. Muench et al., 1998, Plant Physiol. 116: 559-569) have shown that prolamine mRNAs may be anchored to the PB surface via the cytoskeleton. To better understand the mechanism and role of mRNA localization in rice endosperm cells, we studied the subcellular development of prolamine PBs and their relationship with the cytoskeleton in rice endosperm cells. Confocal microscopy of endosperm cells showed that, unlike the glutelin PBs, the developing prolamine PBs are not randomly distributed within the cell, but instead are often enriched in the cortical region of the cell only a few micrometers beneath the plasma membrane. In addition, the peripheral prolamine PBs are closely associated with the cortical microtubule and actin filament networks. The cortical enrichment of rice prolamine protein bodies represents a unique example of endoplasmic reticulum subdomain localization in plant cells. The interaction of this endoplasmic reticulum subdomain with the cytoskeleton provides new insights on the possible mechanism and role of mRNA localization in plants.

Comprehensive proteomic analysis of developing protein bodies in maize (Zea mays) endosperm provides novel insights into its biogenesis

“…Interestingly, 15 actin-related and 10 tubulin-associated cytoskeletal proteins were also identified in the intact PB proteome (Supplementary Table S3). These data support the hypothesis that the cortical actin filament and microtubule networks are involved in anchoring and maintaining the PB–polyribosome–ER membrane complex to the plasma membrane (Muench et al , 2000). Taken together, our data indicated that ribosomes and ER membranes (probably derived from rough ER), as well as the cytoskeleton, although in the peripheral region, are most likely the integral compartments of zein PBs.…”

Production of cecropin A antimicrobial peptide in rice seed endosperm

“…As shown, they are smaller and less spherical than the rhodamine B-stained vesicles (Figure 4B, labelled in red), corresponding to prolamine-containing PBs (PB-I). Rhodamine B hexyl ester binds strongly to rice prolamine and it is regularly used for fluorescent labelling of PB-I [34]. The merged images in Figure 4B clearly show that cecropin A was absent from PB-I, since no colocalization is observed.…”

Dual Regulated RNA Transport Pathways to the Cortical Region in Developing Rice Endosperm

“…The concentration of cytoskeleton and, in particular, actin filaments would serve two functions. First, it would serve as the anchoring site for RNAs transported from the nucleus (Singer, 1992;Bogucka-Glotzer and Ephrussi, 1996;Bloom and Beach, 1999;Muench et al, 2000). Indeed, evidence was obtained showing that prolamine RNAs are retained on prolamine PBs by detergent-resistant, The 10-kD zein RNA is located on the PB-ER, indicating that it contains a cis sorting determinant in the coding sequence.…”