Pair-rule genes were identified and named for their role in segmentation in embryos of the long germ insect @entity238 . Among short germ insects these genes exhibit variable expression patterns during segmentation and thus are likely to play divergent roles in this process. Understanding the details of this variation should shed light on the evolution of the genetic hierarchy responsible for segmentation in @entity238 and other insects. We have investigated the expression of homologs of the @entity238 Pax @entity70169 genes paired, @entity50890 and @entity50890 -neuro in short germ flour beetles and grasshoppers. During @entity238 embryogenesis, paired acts as one of several pair-rule genes that define the boundaries of future parasegments and segments, via the regulation of segment polarity genes such as @entity50890 , which in turn regulates @entity50890 -neuro, a gene expressed later in the developing nervous system. Using a crossreactive antibody, we show that the embryonic expression of Pax @entity70169 genes in both the flour beetle Tribolium and the grasshopper Schistocerca is remarkably similar to the pattern in @entity238 . We also show that two Pax @entity70169 genes, pairberry1 and pairberry2, are responsible for the observed protein pattern in grasshopper embryos. Both pairberry1 and pairberry2 are expressed in coincident stripes of a one-segment periodicity, in a manner reminiscent of @entity238 @entity50890 and @entity50890 -neuro. pairberry1, however, is also expressed in stripes of a two-segment periodicity before maturing into its segmental pattern. This early expression of pairberry1 is reminiscent of @entity238 paired and represents the first evidence for pair-rule patterning in short germ grasshoppers or any hemimetabolous insect.

Pax XXXX genes and the evolution of insect pair-rule patterning.

@entity50890 :: ('38005(Tax:7227)', 'Gene') :: ['gooseberry'] @entity70169 :: ('250154', 'Gene') :: ['group III'] @entity238 :: ('7227', 'Species') :: ['Drosophila']
@entity70169 :: (250154,Gene) :: ['group III']
