3 Chloroplast and Mitochondrial DNAs of Arabidopsis thaliana: Conventional Genomes in an Unconventional Plant

Abstract

Many of the unusual features that make Arabidopsis thaliana such an attractive model system for flowering plants relate, either directly or indirectly, to its unconventional nuclear genome. Of paramount importance, the notably small size of this genome, together with the relative lack of repeated sequences and reduced size of many introns and gene families, directly facilitates efforts to map, isolate, and characterize genes. Indirectly, the small size of the nuclear genome may be related to, perhaps in some measure responsible for, the reduced size of the plant and length of its life cycle, features that considerably enhance its genetic tractability.

The chloroplast and mitochondrial genomes of Arabidopsis have not shared the limelight with its nuclear genome. This is in part because these organellar genomes have not, until recently, been subject to much experimental study and also because they appear, in distinct contrast to the nuclear genome, to be utterly conventional in all important respects. The primary goal of this chapter is to show how the chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) of Arabidopsis are typical of flowering plant organellar genomes in terms of size, organization, content of repeats and genes, gene structure, and, probably, modes of expression and regulation. In terms of direct molecular characterization, the Arabidopsis mitochondrial genome should soon assume primacy among flowering plant mtDNAs, thanks to a genome-sequencing project that is now more than half complete.

A secondary goal of this chapter is to describe what we view as the proper and rightful swing of the...