Regulation of translational initiation in plants.

The abundance of cytosolic mRNA does not necessarily correspond to the quantity of polypeptide synthesized in plant cells. The initiation of mRNA translation is regulated at the global and message-specific levels. mRNAs compete for discriminatory initiation factors that couple the 5'-(7m)GpppN-cap and the 3'-poly(A) tail of the RNA message. The resultant circularization of the mRNA promotes the association of the 43S pre-initiation complex that scans the 5'-leader for the initiation codon of the protein coding sequence. The physiological and developmental regulation of these events governs the level of polypeptide synthesis from endogenous and viral transcripts.