Genes encoding pentatricopeptide repeat (PPR) proteins are not conserved in location in plant genomes and may be subject to diversifying selection

Table 1 Conservation of genes within two regions of Arabidopsis chromosome 1.

Location	4.3 Mb region²	23 Mb region³
Number of genes/ORFs	19	18
PPR-encoding genes	3	4
Conserved genes	8	8
Hypothetical proteins	2 (+ 1 transposon)	1
% conserved genes¹ (all, discounting PPRs)	50	57

¹ Percentage of conservation is calculated based on number of genes conserved out of the total number of genes, including hypothetical proteins but not including PPR genes. For example, in the 4.3 Mb region, this is 9 conserved genes out of (19 genes/ORFs -3 PPR-encoding genes) or 9 ÷ 16 = 56%. PPR genes are discounted due to the difficulty in concretely matching PPRs by sequence comparison, and also because of the variability in number and location of PPR genes. Hypothetical genes are annotated according to the Arabidopsis annotation according to TAIR.
² The 4.3 Mb region includes genes DDF1 through At1g12780.
³ The 23 Mb region includes genes DDF2 through At1g63180.

ISSN: 1471-2164