Identification and functional analysis of promoters of heat-shock genes from the fall armyworm, Spodoptera frugiperda

The functional information on heat-shock proteins (Hsp) and heat-shock promoters from an important agricultural insect pest, Spodoptera frugiperda, is still lacking. We conducted a genome-wide identification of Hsp genes and identified a total of 21 genes belonging to four major insect Hsp families (small heat-shock proteins, Hsp60, Hsp70, and Hsp90) in S. frugiperda. Expression of most of S. frugiperda (SfHsp) genes could be detected in Sf9 cells, embryos and larval tissues of S. frugiperda. The heat-inducible activity of heat-shock promoters from several SfHsp genes was tested in Sf9 cells and embryos. The promoter of SfHsp70D showed the high constitutive activity in cell line and embryos, while the activity of SfHsp20.15 and SfHsp20.71 promoters was most dramatically induced in Sf9 cells and embryos. In embryos, the heat-induced activity of SfHsp20.71 and SfHsp70D promoters outperformed commercially used ie1 and ie2 promoters. The heat-induced activity of SfHsp70D and SfHsp19.07 promoters were more robust than ie2 promoter in Sf9 cells. These SfHsp promoters with high basal activity or with heat-induced activity from low basal activity, could be used in S. frugiperda or other lepidopteran insects for many applications including transgenesis and genome editing.