Eukaryotic protein production in designed storage organelles.

Background: Protein bodies (PBs) are natural endoplasmic reticulum (ER) or vacuole plant-derived organelles that stably accumulate large amounts of storage proteins in seeds. The proline-rich N-terminal domain derived from the maize storage protein gamma zein (Zera) is sufficient to induce PBs in non-seed tissues of Arabidopsis and tobacco. This Zera property opens up new routes for high-level accumulation of recombinant proteins by fusion of Zera with proteins of interest.

The direct activation of MIK, a germinal center kinase (GCK)-like kinase, by MARK, a maize atypical receptor kinase, suggests a new mechanism for signaling through kinase-dead receptors.

Signaling by receptor protein kinases (RPKs) involves their dimerization and transphosphorylation. However, atypical RPKs with kinase-defective domains have been described recently. Some of them are essential for proper signaling in animal systems, although the precise mechanism involved is unknown in most cases.