Expression driven by a construct that carried 300 bp of the predicted
tiar-1 promoter, gfp, 1227 bp of the
tiar-1 ORF and 485 bp of the downstream 3'UTR (PStiar-1gfp::
tiar-1): This construct was expressed in the soma in a pattern similar to that observed for the native protein by immunostaining (Expr11172), but it was not expressed in the germline, possibly because of natural transgene silencing in this tissue (Kelly et al., 1997). It is also possible that the construct was lacking a DNA region required for germline expression. Therefore the authors generated a second construct carrying 1997 bp of the
tiar-1 promoter, 1966 bp of the
tiar-1 genomic sequence, gfp and 1500 bp of the
tiar-1 3'UTR (PLtiar-1tiar-1::gfp). PLtiar-1TIAR-1::GFP expression was similar to the expression of the native protein as measured by antibody staining in soma and germline (Expr11172), and also to the expression of the previous transgene. PLtiar-1TIAR-1::GFP associated with perinuclear granules. PLtiar-1TIAR-1::GFP co-localized with the P granules marker PGL-1.Occasionally, nuclear expression of PLtiar-1TIAR-1::GFP was observed in some embryos. Similar to what the authors observed using TIAR-1 antibody in inmunostainings, PLtiar-1TIAR-1::GFP expression appears reduced in the most proximal oocytes (-1 and -2 oocytes). This lower expression of TIAR-1 transgene continues through early embryogenesis. Because TIAR-1 is not always associated with P granules using immunostainings and/or in transgenic animals, the authors suggest that its association with these structures might be transient or sensitive to certain conditions or manipulations.