Figure 2.

Possible RNA localization pathways to cortical ER subdomains. Schematic representation of the distinct targeting pathways leading from the nucleus to the cortical ER. In addition to two regulated RNA pathways for prolamine and glutelin mRNA targeting, which require specific zipcode signals, there is evidence for the existence of a default pathway leading to the cisternal ER. Also depicted are the changes in RNA localization seen in the glup mutants. Based on the analysis of glup mutants, the three RNA pathways are not independent but are interrelated. This model does not distinguish the possibility that different RNAs reside in the same RNA transport particle and then segregate to PB-ER and cisternal ER or whether the three RNA transport pathways denote transport particles containing specific RNAs.