Characterization of the targeted nuclear accumulation of GFP within the cells of transgenic plants

The soluble proteins of the nucleoplasm are synthesized on cytoplasmic ribosomes. Proteins larger than about 40 kDa are post-translationally targeted to the nucleus via energy-dependent processes, passing through the nuclear pore complex into the nucleoplasm. Targeting involves nuclear localization signals (NLSs) found within the primary sequences of the imported proteins. In higher plants, information has come primarily from study of proteins carrying 'classical' NLSs, comprising stretches of basic amino acids, and has required assays to measure nuclear uptake both in vitro and in vivo . In general, these assays are not entirely satisfactory; they are either technically demanding, are of limited accuracy and statistical rigor, or are unsuitable for in vivo applications.