Bao and Xu BMC Genomics 2011, 12:224 http://www.biomedcentral.com/1471-2164/12/224 Page 5 of 14 Figure 2 Classification of the unique sequence from the SSH according to Gene Ontology criteria. Gene Ontology analysis was carried out on the transcripts isolated from the two SSH libraries. The biological process combined graph was made based on ontology level 2. lipoprotein metabolism. Lipase (HarNP-1246) partici- pates in the lipid degradation process. Stress resistance Eight genes were assigned to the stress resistance cate- gory (Table 1B), all up-regulated at diapause initiation. Hsp70 (HarDP-A355) acts as a molecular chaperone to protect cellular proteins from denaturation and contri- butes to the cold tolerance of insects [13]. Another group of transcripts that was up-regulated at diapause initiation was related to antioxidation: ferritin (HarDP- C556), ferritin light chain (HarDP-C941), MnSOD (HarDP-B1408), glutathione S-transferase (GST, HarDP- A22) and bombyrin (HarDP-A112). The last two tran- scripts activated in response to stress are related to DNA repair: Rad23 (HarDP-A345) and integrator com- plex subunit 3 (HarDP-C509). Rad23 functions in UV- damaged DNA repair post-replication, and integrator