Transposable elements (TEs) are highly abundant in plant genomes. Environmental stress is one of the critical stimuli that activate TEs. We analyzed a heat-activated retrotransposon named ONSEN in cruciferous vegetables. The multiple copies of ONSEN-like elements (OLEs) were found in all the cruciferous vegetables that were analyzed. The copy number of OLE was abundant in Brassica oleracea, which includes cabbage, cauliflower, broccoli, Brussels sprout, and kale. Phylogenic analysis demonstrated that some OLEs transposed after the allopolyploidization of parental Brassica species. Furthermore, we found that the increasing number of OLEs in B. oleracea appeared to be induced transpositional silencing by epigenetic regulation, including DNA methylation. The results of this study would be relevant to the understanding of evolutionary adaptations to thermal environmental stress in different species.

To elucidate the cellular immune response to coronavirus disease (COVID-19) among children, we assessed cellular immunity in 8 children post-vaccination for COVID-19 and 11 children after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, using the T-SPOT®.COVID assay for both the spike (S) and nucleocapsid (N) proteins. In the vaccinated group, the T-SPOT®.COVID assay for the S protein yielded positive results in all eight children. In contrast, in the post-infection group, the assay for the N protein was positive in 5 of 11 children, with 3 of these 5 children requiring hospital admission, including 2 who needed mechanical ventilation. Therefore, the T-SPOT®.COVID assay is valuable for assessing cellular immunity against COVID-19, and most children infected with COVID-19 may not develop such immunity unless the disease severity is significant.