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Abstract
Post-endosymbiotic evolution has produced numerous definable adaptations in higher plants. In this study, features including protein dual targeting to organelles, expansion of nuclear gene families and nuclear-organellar signaling are described. Protein dual targeting gives the cell the capability to send a single gene product to multiple organelles. Alternative translation initiation (aTI) is one way to achieve dual targeting, in some cases utilizing non-AUG initiation codons. In Arabidopsis, DNA polymerase ( AtPOLγ2) uses aTI to localize distinct gene products to organelles. To understand the regulation of aTI, Polγ2 was used as a model to investigate both cis- and trans-acting features of the process. In an attempt to study more about dual targeting proteins, the SVM-based prediction program dPred was designed to test prediction feasibility. Around 2500 nuclear-encoded gene products were predicted to be dual targeted using dPred with an accuracy of 68%. Changes in the mitochondrial genome produced by illegitimate recombination activity have also been studied. The associated changes in mitochondrial gene expression give rise to several altered phenotypes including male sterility, leaf variegation, modified leaf morphology, stunted plant growth and enhanced response to heat. Gene expression analysis of the several altered phenotypes revealed that mitochondria might play an important role in influencing plastid developmental functions, cell division processes and plant stress responses.
