Fig. 6

Fig. 6 SBU2 phenotype is the result of a non-sense mutation on spt6 gene. SBU2 maps to linkage group 21 between Z7809 and Z10432 (A). Sequencing analysis revealed a C to T transition at the 3931st nucleotide of the coding sequence of the spt6 gene (B). Predicted Spt6 protein structure in wild-type, pan^m313 and pan^SBU2 mutant embryos (C). The premature stop codon in SBU2 is predicted to produce a truncated protein which lacks SH2 domain (C). The defects in homozygous SBU2 embryos can be rescued by injection of spt6 mRNA (G). Microinjection of spt6 morpholino into the progeny from intercrosses of wild-type siblings of SBU2 heterozygotes, phenocopies SBU2 mutants (H). However, in some wild-type stocks, the phenotype upon injection of spt6 morpholino is much weaker (I) and resembles pan phenotype (F). Panels D, E, G, and H are 27-h-old embryos; panels F and I are 48-h-old embryos. Asterisk denotes stop codon in panel B.