The maize desynaptic1 mutation disrupts meiotic chromosome synapsis

• Published in: Developmental genetics 1997, Vol.21 (2), p.146-159
• Main Authors: Golubovskaya, I.N, Grebennikova, Z.K, Auger, D.L, Sheridan, W.F
• Format: Article
• Language: English
• Subjects: ABNORMAL SYNAPSIS; ALLELES; ALLELISM; APAREAMIENTO CROMOSOMICO; APPARIEMENT CHROMOSOMIQUE; CHIASMATA; CHROMOSOME; CHROMOSOME PAIRING; chromosome synapsis; CHROMOSOMES; CROMOSOMAS; DSY1 LOCUS; FENOTIPOS; FOLDBACK SYNAPSIS; GENE; GENES; GENETIC INHERITANCE; HEREDITE; HERENCIA GENETICA; INDUCED MUTATION; LOCI; LOCUS; maize; MEIOSE; MEIOSIS; MUTACION INDUCIDA; MUTANT; MUTANTES; MUTANTS; mutation; MUTATION PROVOQUEE; NONHEMOLOGOUS SYNAPSIS; PHENOTYPE; PHENOTYPES; PROPHASE; SEGREGACION; SEGREGATION; UNIVALENT; ZEA MAYS
• ISSN: 0192-253X; 1520-6408
• DOI: 10.1002/(SICI)1520-6408(1997)21:2<146::AID-DVG4>3.0.CO;2-7

In most eukaryotes, homologous chromosomes undergo synapsis during the first meiotic prophase. A consequence of mutations that interfere with the fidelity or completeness of synapsis can be failure in the formation or maintenance of bivalents, resulting in univalent formation at diakinesis and production of unbalanced spores or gametes. Such mutations, termed desynaptic mutations, can result in complete or partial sterility. We have examined the effect of the maize desynaptic 1-9101 mutation on synapsis, using the nuclear spread technique and electron microscopy to examine microsporocytes ranging from early pachytene until the diplotene stage of prophase I. Throughout the pachytene stage, there was an average of about 10 sites of lateral element divergence (indicating nonhomologous synapsis), and during middle and late pachytene, an average of two and three sites 4 foldback (intrachromosomal) synapsis, per mutant nucleus, respectively. By the diplotene stage, the number of sites of lateral element divergence had decreased to seven, and there was an average of one foldback synapsis site per nucleus. Lateral element divergence and foldback synapsis were not found in spread pachytene nuclei from normal plants. These results imply that the normal expression of the dsy 1 gene is essential for the restriction of chromosome synapsis to homologues. The abundance of nonhomologous synapsis and the persistence of extended stretches of unsynapsed axial elements throughout the pachytene stage of dsy 1-9101 meiocytes suggests that this mutation disrupts both the fidelity of homology search and the forward course of the synaptic process. This mutation may identify a maize mismatch repair gene