Constitutive and Regulated Induced Proliferation Pathways

Recent reviews pertaining to the self-replicating model (Purdue and Lazarow 2001; Lazarow 2003) have included new information on the sequential uptake of specific peroxins, while strongly adhering to basic non-involvement of ER in the process of peroxisomal biogenesis. The basic tenant is that pre-existing peroxisomes are the source for the constitutive, steady-state production of daughter peroxisomes during normal cell division (Fig. 1, dashed lines). Accordingly, pre-existing immature peroxisomes mature/become elaborated through direct acquisition of matrix and membrane proteins post-translationally from the cytosol. Although not cited in either of the two reviews, much evidence in support of direct post-translational insertion of matrix and membrane proteins has come from studies with pre-existing plant peroxisomes (e.g. Brickner et al. 1997; Lisenbee et al. 2005; Mullen et al. 1999; Murphy et al. 2003; Pool et al. 1998; Hunt and Trelease 2004; Sparkes et al. 2005). Such acquisitions are clearly a manifestation of plant peroxisomal growth (enlargement). Specific examples are given in Sects. 3.2 and 5.1.

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