NCL-1 acting as a restriction factor for nucleolar size and rRNA expression is associated with nucleolar protein, FIB-1.

<p>(A) Differential contrast interference (DIC) microscopy of the gonads of the wild-type (wt) or <i>ncl-1(e1942)</i> worms. Numbers mark the different oocytes and arrowheads indicate the location of nucleoli. Double arrowheads indicate the nucleoli of germ cells. Insets at lower left are enlargement from the square areas of oocytes. Sp, spermatheca. Scale bar, 20 μm. (B) Diameters of the nucleoli in the gonadal cells, as shown in (A), were quantitatively determined. Asterisks signify differences between the two worms: ***<i>P</i> < 0.0001; <i>n</i> = 8–14 gonad arms. (C) DIC microscopy of the blastomeres of wild-type (wt) and the <i>ncl-1</i> embryos, with or without <i>fib-1</i> RNAi. Each blastomere is indicated as ABa, ABp, EMS and P. Insets represent enlarged versions of the boxed regions of ABp cells to highlight the nucleoli. Scale bar, 20 μm. (D) Quantitative representation of the results shown in (C), which illustrates the distribution of nucleolar areas in the four blastomeres. Asterisk signifies difference between the indicated strains: *<i>P</i> < 0.05; <i>n</i> ≥ 31 embryos. (E) Knockdown of <i>fib-1</i> was done in the indicated worms. The expression of Actin (lower panel) and the endogenous FIB-1 (upper panel) were examined by Western blot analysis. (F) RT-qPCR analysis of 26S rRNA expression in the indicated strains of worms as shown in (E) *<i>P</i> < 0.05; ***<i>P</i> < 0.001; ns, no significant; n = 3.