Table 1.

Factors required for the piRNA pathway

Protein	Physical interactions	Fertility of mutants	Homologs in other species	References
Primary piRNA pathway
Yb	Vret, Armi	Female sterile	ND	[28]
		Male sterile
Zucchini (Zuc)	Aub	Female sterile	Mouse: MitoPLD	[38]
			MMZuc or Pld6
Armitage (Armi)	Yb, Piwi, Vret	Female sterile	Mouse: Mov10L1	[28,32]
		Partial male sterile
Sister of Yb (SoYb)	Vreta	ND	ND	[28]
Vreteno (Vret)	SoYBa, BoYBa, YB, Aub, Armi, AGO3, Piwi	Female sterile	Mouse: Tdrd1	[28,32]
		Male sterile
Gasz	Karyβ3a	Female sterile	Mouse: Gasz	[34]
Shutdown (Shu)	ND	ND	Mouse: Fkbp6	[29]
Hen1	Piwi	Fertile	Mouse: Hen1	[39]
Brother of Yb (BoYb)	Vreta	Partial female sterile	Mouse: Tdrd12	[28]
Secondary piRNA pathway
Krimper (Krimp)	ND	Female sterile	ND	[40]
Aubergine (Aub)	AGO3, Qin/Kumo, Squ, Tej, Vret, Zuc, Tap	Female sterile	Mouse: Mili	[41,42]
		Male sterile
AGO3	Aub,Vret	Female sterile		[32,42]
		Partial male sterile
Vasa	Qin/Kumo, Tej, Tap	Female sterile	Mouse: Mvh, B. mori: Vasa	[41,43]
		Male sterile
Spindle-E (Spn-E)	Qin/Kumo, Tej, Tap	Female sterile	Mouse: Tdrd9	[41,43]
		Male sterile
Papi	ND	ND	Mouse: Tdrd2	[44]
Tejas (Tej)	Aub, Spn-E, Vasa, Tap	Female sterile,	Mouse: Tdrd5	[43]
		Male fertile
Tapas, (Tap)	SpnE, Aub, Tej, Vasa	Fertile	Mouse: Tdrd7	[45]
Qin/Kumo	HP1, Aub, Piwi, Spn-E, Vasa	Female sterile	Mouse: Rnf17	[41,42]
TE Transcriptional silencing
Piwi	Hen1, Armi, Arx, HP1, Qin/Kumo,Vret	Female sterile		[39,46]
		Male sterile
Mael		Female sterile	Mouse: Maelstrom	[31,40]
		Male sterile
Asterix (Arx)	Piwi	Female sterile	Mouse: Gtsf1	[47]
		Male sterile		[39]

^aFlybase information.