Final answer:
Genes not typically induced during the UPR are those not involved with protein folding, degradation, or modification, such as unrelated metabolic pathways or siderophore biosynthesis, according to studies like Molina et al. (1999) and unpublished data on Bacillus subtilis HR23.
Step-by-step explanation:
During the unfolded protein response (UPR), certain types of proteins are not typically induced. The UPR primarily focuses on upregulating genes that aid in protein folding, degradation, and modification to alleviate stress within the endoplasmic reticulum (ER). Therefore, genes that are not directly related to protein quality control, such as those involved in unrelated metabolic pathways, are likely not induced. For instance, studies such as Molina et al. (1999) found that wheat genes encoding two types of PR-1 proteins are pathogen-inducible but do not respond to activators of systemic acquired resistance, indicating that these proteins do not typically participate in the UPR. Additionally, during the UPR, there can be a general downregulation of overall protein synthesis to reduce the load on the ER, involving the translational attenuation mechanism where eukaryotic initiation factor-2 (eIF-2) may play a role. Proteins related to functions such as siderophore biosynthesis, as mentioned in the reference to unpublished data regarding the adaptive response of Bacillus subtilis HR23 mutant to a new genetic code, are examples of proteins whose genes may be downregulated during the UPR.