Chapter 5 Genetic Analysis of Apomixis - cimmyt

From Sexuality la Apomixis: Molerolar and Geneli, Approa'hes 197Figure 12.3 The R-Novojo (R-n,) dominantmaker system for embryo and endosperm.(a) Bath embryo and endosperm carry the R-njmarker and show anthocyanin pigmentation. [b}Only the endosperm carries the R-nj marker while theembryo does not, i.e., is nof pigmented. This kernelwas obtained from a mixed pollination throughheterofertilizatian, but a parthenogenetically formedembryo will also lack the paternal R-nj marker.~ nP "GUSmin"~ Enhancer DetectionArabidopsis gene~ .. .J ~ c:O:---fuOs elementstigmo-specificenhancerGene Trapping((::::;OPSiS genestigma-specificenhancer~Ds elementFigure 12.4 The principle of enhancer detection and gene trapping.la) an inflorescence of an enhancer detector transpasant with reporter geneactivity specifically in stigmatic papillar cells of mature flowers. (b) enhancerdetection relies an a Ds element carrying a reporter gene (GUS) under the (ontrolof a minimal promoter (Pmin)' If the Pmin is influenced by genomic cis-regulatorysequences, e.g., a stigma-specific enhancer, the GUS gene isexpressed in a lissue- ond time-specific manner in the sameway as the gene that is usually controlled by the detectedenhancer. (e) gene traps are a modification of enhancerdetectors relying on splice acceptor (SA) sites in all threereading frames. If the gene trap inserts into a transuiplionsunit frans-splicing can produce a GUS fusion protein Ihatreflects the expression of the detected gene.MiFigure 12.5 Enhancer detector transposant with GUSexpression restricted to the megagametophyte.Abbreviations: Ch, chalaza; Mi, micropyle; ES, embryo sac; 01,outer integument; II, inner integument.