Surveying the Lettuce Genome: Genome-wide Identification of Hsfs and Hsps in Response to UV and High Light Stress

Background Heat shock factors (Hsfs) and Heat shock proteins (Hsps) belong to an essential group of molecular regulators involved in controlling cellular processes under normal and stress conditions. The role of Hsfs and Hsps is well known in model plant species under diverse stress conditions. However, in lettuce (Lactuca sativa), a highly consumed vegetable crop grown in the field and in hydroponic systems, the role of these gene families in response to artificial light is not well characterized. Results Using a genome-wide analysis approach, we identified 32 Hsfs and 22 small heat shock proteins (LsHsps) in lettuce, some of which do not have orthologous in Arabidopsis, poplar, and rice. LsHsp60s, LsHsp90s, and LsHsp100s are highly conserved among dicot and monocot species. Surprisingly, LsHsp70s have three times more members than Arabidopsis and two times more than rice. Genome triplication might have contributed to the increased number of LsHsp70s genes. Chromosomal distribution analysis shows larger tandem repeats of LsHsp70s genes in Chr1, Chr7, Chr8, and Chr9. At the transcriptional level, some genes of the LsHsfs, LsHsps, LsHsp60s, and LsHsp70s families were highly responsive to UV and high light stress, in contrast of LsHsp90s and LsHsp100s which did not respond to a light stimulus. Conclusions Our genome-wide analysis provides a detail identification of Hsfs and Hsps in lettuce. Chromosomal location and syntenic region analysis together with our transcriptional analysis under different light conditions provide candidate genes for breeding programs aiming to produce lettuce varieties able to grow healthy under hydroponic systems that use artificial light.