For sustainable crop cultivation in the face of global warming, it is important to unravel the genetic mechanisms underlying plant adaptation to a warming climate and apply this information to breeding. Thermomorphogenesis and ambient temperature signaling pathways have been well studied in model plants, but little information is available for vegetable crops. Here, we investigated genes responsive to warming conditions from two Brassica rapa inbred lines with different geographic origins: subtropical (Kenshin) and temperate (Chiifu). Genes in Gene Ontology categories “response to heat”, “heat acclimation”, “response to light intensity”, “response to oxidative stress”, and “response to temperature stimulus” were upregulated under warming treatment in both lines, but genes involved in “response to auxin stimulus” were upregulated only in Kenshin under both warming and minor-warming conditions. We identified 16 putative high temperature (HT) adaptation-related genes, including 10 heat-shock response genes, 2 transcription factor genes, 1 splicing factor gene, and 3 others. BrPIF4, BrROF2, and BrMPSR1 are candidate genes that might function in HT adaptation. Auxin response, alternative splicing of BrHSFA2, and heat shock memory appear to be indispensable for HT adaptation in B. rapa. These results lay the foundation for molecular breeding and marker development to improve warming tolerance in B. rapa.

Caenorhabditis elegans C09F5.1 is a nematode-specific gene that encodes a type II transmembrane protein containing the BRICHOS domain. The gene was isolated as a heat-sensitive mutant, but the function of the protein remained unclear. We examined the expression pattern and subcellular localization of C09F5.1 as well as its roles in thermotolerance and chaperone function. Expression of C09F5.1 under heat shock conditions was induced in a heat shock factor 1 (HSF-1)–dependent manner. However, under normal growth conditions, most cells types exposed to mechanical stimuli expressed C09F5.1. Knockdown of C09F5.1 expression or deletion of the N-terminal domain decreased thermotolerance. The BRICHOS domain of C09F5.1 did not exhibit chaperone function unlike those of other proteins containing this domain, but the domain was essential for the proper subcellular localization of the protein. Intact C09F5.1 was localized to the Golgi body, but the N-terminal domain of C09F5.1 (C09F5.1-NTD) was retained in the ER. C09F5.1-NTD delayed paralysis by beta-amyloid (1-42) protein (Aβ₄₂) in Alzheimer’s disease model worms (CL4176) and activated the unfolded protein response (UPR) by interacting with Aβ₄₂. An intrinsically disordered region (IDR) located at the N-terminus of C09F5.1 may be responsible for the chaperone function of C09F5.1-NTD. Taken together, the data suggest that C09F5.1 triggers the UPR by interacting with abnormal proteins.