d-Tryptophan enhances the reproductive organ-specific expression of the amino acid transporter homolog Dr-SLC38A9 involved in the sexual induction of planarian Dugesia ryukyuensis

Table 1 Dr-SLC38A9 RNAi knockdown during sexual induction

Treatment period	Test food^a	Number of worms developing a pair of ovaries (%)^b	Number of worms developing copulatory apparatus (%)^b	Number of worms developing a genital pore (%)^b
Week 4	EGFP dsRNA	29/29 (100)	21/29 (72.4)	0/29 (0)
Week 4	Dr-SLC38A9 dsRNA	22/29 (75.9)*^c	5/29 (17.2)**^d	0/29 (0)
Week 6	EGFP dsRNA	18/18 (100)	18/18 (100)	14/18 (77.8)
Week 6	Dr-SLC38A9 dsRNA	19/19 (100)	15/19 (78.9) n.s.^e	4/19 (21.1)***^f

^aAsexual worms were fed minced B. brunnea worms supplemented with EGFP (control), daily or Dr-SLC38A9 dsRNA for up to 6 weeks (summarized in Fig. 4)
^bDevelopment of ovaries, copulatory apparatus, and a genital pore were observed externally using a stereoscopic microscope
^cStatistical significance was calculated using one-sided Fisher’s exact test (*P = 0.0052)
^dStatistical significance was calculated using the Chi-squared test (**х² (1, N = 58) = 17.8, P < 0.001)
^eStatistical significance was calculated using Fisher’s exact test (P = 0.059, n.s.: not significant)
^fStatistical significance was calculated using the Chi-squared test with Yates’ continuity correction (***х² (1, N = 37) = 9.7, P = 0.0018)

ISSN: 2056-306X