Effect of GST knock-down by RNAi on life span of C. elegans Bristol-N2. The life span of control animals fed bacteria transformed with insert-free vector (open symbols) was recorded simultaneously with that of animals in which individual GSTs (listed in the Figure) were knocked down by RNAi (closed symbols). Panels A, C, E, G, and I show means of independent life span determinations plotted separately and denoted by distinct symbols in panels B (4 independent experiments), D (2 experiments), F (4 experiments), H (2 experiments), and J (2 experiments), respectively. Each survival curve shown in panels B, D, F, H, and J represents a population of 100 or 150 worms. For each GST, data from the individual experiments were analyzed by Cox regression. After adjusting for inter-experiment variability and applying the Holm correction for multiple comparisons (Holm, 1979), RNAi targeted to gst-5 was found to be different from control at P = 4.8 × 10−21, gst-6 at P = 0.09, gst-8 at P = 0.27, gst-10 at P = 4.8 × 10−20, and gst-24 at P = 0.14.