Maize Genetics Cooperation Newsletter

maize gene review

Authors: Chung-Ju Rachel Wang, Inna Golubovskaya, Olivier Hamant, W. Zacheus Cande, University of California, Berkeley, CA. 94720-3200

DOI/

Review: pending

Pub date: May 2009

Name: afd1--absence of first division1

Synonyms: si618011B05, rec8

Chromosome 6 bin 6.05
Genome Browser via cDNA AY788900 | 60202504

Function: early meiosis

Summary: The absence of first division1 mutant originally received its name because the meiotic first (reduction) division is replaced by an equational division (Golubovskaya and Mashnenkov 1975). In a truncated allele (afd1-1) and a null allele (afd1-2), early meiotic prophase chromosome structure is altered; there is little axial element formation, no bouquet formation, few RAD51 foci are loaded onto chromosomes and neither pairing, synapsis nor recombination takes place. In weaker alleles (afd1-3, and afd1-4), leptotene chromosomes form, and the elongation of the axial element and bouquet formation are partially restored; however, pairing and synapsis are abnormal. As a result, all four afd1 mutant alleles exhibit 20 univalents that separate equationally at metaphase I, leading to male and female sterility. In wild-type meiocytes, AFD1 protein is recruited to chromosomes before leptotene, and is localized on the axial element during zygotene and pachytene (Golubovskaya et al. 2006). afd1 gene is epistatic to dsy1, as1, and dv1 (Golubovskaya et al. 1993).

Images: Wild-type and afd1-1 chromosomes at pachytene and metaphase I stages stained by DAPI showing in afd1 mutant, (b) altered chromosome structures and (d) 20 univalents arrayed at the metaphase I plate with bipolar orientation.

First reported: Golubovskaya and Mashnenkov 1975

Key Alleles: from Golubovskaya et al 2006

afd1-1, the original reference allele. A G-->A point mutation in intron 16 introduces a stop codon.

afd1-2::Mu; null allele, Mu inserted upstream of first exon.

afd1-3::Mu; leaky allele, Mu inserted into 3rd intron.

afd1-4::Mu; leaky allele, Mu inserted into 1st intron.

Map Location

Uncovered by TB-6Lc (Golubovskaya et al 2003); at 6L.98 by in situ hybridization(Wang et al. 2006); closely linked to tdy1; near umc2059 and bnlg1136 (Golubovskaya et al. 2006).

Gene Product

REC8 homolog; component of the cohesin complex at centromeres. Required for SGO1 recruitment to centromeres (Golubovskaya et al. 2006).

Expression

In leaves, tassel and ear, less in roots and very early leaves.

Epistatic to

dsy1, as1, and dv1 (Golubovskaya et al. 1993).

References

Golubovskaya I, Mashnenkov AS (1975) Genetic control of meiosis. I. meiotic mutation in corn (Zea mays L.) afd, causing the elimination of the first meiotic division. Genetika 11:11-17.

Golubovskaya I, Grebennikova ZK, Avalkina NA, Sheridan WF (1993) The role of the ameiotic1 gene in the initiation of meiosis and in subsequent meiotic events in maize. Genetics 135:1151-1166. PUBMED

Golubovskaya I, Sheridan W, Harper LC, Cande WZ (2003) Novel meiotic mutants of maize identified from Mu transposon and EMS mutant screens. MNL 77:10-13

Golubovskaya I, Hamant O, Timofejeva L, Wang CR, Braun D, Meeley R, Cande WZ (2006) Alleles of afd1 dissect REC8 functions during meiotic prophase I. Journal of Cell Science 119: 3306-3315. PUBMED

Wang CR, Harper L, Cande WZ (2006) High-resolution single-copy gene fluorescence in situ hybridization and its use in the construction of a cytogenetic map of maize chromosome 9. The Plant Cell 18:529-544. PUBMED

Links: MGD afd1 NCBI: afd1 UniProt: Q3BCU1