Regulation and Function of Scr, exd, and hth in the Drosophila Salivary Gland

[摘要] SalivaryglandformationintheDrosophilaembryoisdependentonthehomeoticgeneSexcombsreduced(Scr).WhenScrfunctionismissing,salivaryglandsdonotform,andwhenSCRisexpressedeverywhereintheembryo,salivaryglandsforminnewplaces.Scrisnormallyexpressedinallthecellsthatformthesalivarygland.However,asthesalivaryglandinvaginates,ScrmRNAandproteindisappear.Homeoticgenes,suchasScr,specifytissueidentitybyregulatingtheexpressionofdownstreamtargetgenes.Formanyhomeoticproteins,targetgenespecificityisachievedbycooperativelybindingDNAwithcofactors.Therefore,itislikelythatSCRalsorequiresacofactor(s)tospecificallybindtoDNAandregulatesalivaryglandtargetgeneexpression.Here,weshowthattwohomeodomain-containingproteinsencodedbytheextradenticle(exd)andhomothorax(hth)genesarealsorequiredforsalivaryglandformation.exdandhthfunctionattwolevels:(1)exdandhtharerequiredtomaintaintheexpressionofScrinthesalivaryglandprimordiapriortoinvaginationand(2)exdandhtharerequiredinparallelwithScrtoregulatetheexpressionofdownstreamsalivaryglandgenes.WealsoshowthatScrregulatesthenuclearlocalizationofEXDinthesalivaryglandprimordiathroughrepressionofhomothorax(hth)expression,linkingtheregulationofScractivitytothedisappearanceofScrexpressionininvaginatingsalivaryglands.

[学科分类] 生物科学（综合）

[关键词] extradenticle;Drosophila;homeotic genes;homothorax;salivary gland;Sex combs reduced.