Analysis of expressed sequence tags in Brassica napus cotyledons damaged by crucifer flea beetle feeding

The molecular basis of canola ( Brassica napus L.) susceptibility to the crucifer flea beetle (FB, Phyllotreta cruciferae Goeze) was investigated by comparing transcript representation in FB-damaged and undamaged cotyledons. The B. napus cotyledon transcriptome increased and diversified substantially after FB feeding damage. Twenty-two genes encoding proteins with unknown function, six encoding proteins involved in signaling, and a gene encoding a B-box zinc finger transcription factor were moderately or strongly changed in representation with FB feeding damage. Zinc finger and calcium-dependent genes formed the largest portion of transcription factors and signaling factors with changes in representation. Six genes with unknown function, one transcription factor, and one signaling gene specific to the FB-damaged library were co-represented in a FB-damaged leaf library. Out of 188 transcription factor and signaling gene families screened for "early" expression changes, 16 showed changes in expression within 8 h. Four of these early factors were zinc finger genes with representation only in the FB-damaged cotyledon. These genes are now available to test their potential at initiating or specifying cotyledon responses to crucifer FB feeding.