Short interspersed nuclear elements (SINEs) are non-long terminal repeat retrotransposons that are highly abundant, heterogeneous, and mostly not annotated in eukaryotic genomes. We developed a tool designated SINE-Finder for the targeted discovery of tRNA-derived SINEs. We analyzed sequence data of 16 plant genomes, including 13 angiosperms and three gymnosperms and identified 17,829 full-length and truncated SINEs falling into 31 families showing the widespread occurrence of SINEs in higher plants. The investigation focused on potato (Solanum tuberosum), resulting in the detection of seven different SolS SINE families consisting of 1489 full-length and 870 59 truncated copies. Consensus sequences of full-length members range in size from 106 to 244 bp depending on the SINE family. SolS SINEs populated related species and evolved separately, which led to some distinct subfamilies. Solanaceae SINEs are dispersed along chromosomes and distributed without clustering but with preferred integration into short A-rich motifs. They emerged more than 23 million years ago and were species specifically amplified during the radiation of potato, tomato (Solanum lycopersicum), and tobacco (Nicotiana tabacum). We show that tobacco TS retrotransposons are composite SINEs consisting of the 39 end of a long interspersed nuclear element integrated downstream of a nonhomologous SINE family followed by successfully colonization of the genome. We propose an evolutionary scenario for the formation of TS as a spontaneous event, which could be typical for the emergence of SINE families.

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Key Points• The expression of CD16 by immature slanDCs equips these cells with a unique capacity to handle immune complexes.• CD16 expression on slanDCs is rapidly downregulated during maturation by activation of ADAM10 and ADAM17. We show that CD16 is rapidly shed from the surface of maturing slanDCs, resulting from the combined action of the metalloproteinases ADAM10 and ADAM17. In conclusion, these data provide strong evidence that slanDCs play an important role in IC-driven immune responses. (Blood. 2013;121(18):3609-3618)