Research Theme within School of Biosciences: Molecular and Cell Biology
Organisation and behaviour of chromosomes in plant meiosis
My research interests are concerned with meiosis, a highly conserved pathway, by which haploid gametes are formed following a double cell-division process. Our laboratory is interested in chromosome behaviour during pairing, recombination and synapsis in plant meiosis. We use molecular cytogenetic and immunolocalisation techniques combined with the molecular resources available for Arabidopsis molecular biology, to investigate aspects of this complex process that continues to be poorly understood.
We (Professor Franklin and I) have recently been awarded a LOLA award to transfer our Arabidopsis knowledge to investigate meiosis in barley and to find ways to manipulate crossover frequency and distribution in this cereal (see Professor Chris Franklin web-page for details). I am also co-ordinator for an EU collaborative project
Currently my research falls into 3 areas:
1. Telomere biology in Arabidopsis We are investigating how homologous telomeres pair during early meiotic prophase. Recent attention has been paid to the bouquet, a nearly universal event during which telomeres move and cluster in early prophase. We are looking at pairing in telomere deficient plants in order to understand the significance of this early step in the meiotic pathway.
2. Genetic and cytogenetic investigation of homoeologous pairing and recombination in B. Napus (AACC). Breeders wishing to introduce new characteristics into the B. Napus (oil seed rape) crop are creating synthetic lines by crossing B. Oleracea with B. Rapa. In natural B. Napus plants pairing control is strict; (A/A and C/C) whereas in synthetics pairing control is less strict (A/C) and can lead to unstable progeny and loss of fertility. We are investigating the nature of this problem.
3. Evolution of sex chromosomes in the plant genus Silene. I collaborate with DA Filatov (Oxford). Our joint research interests are concerned with evolution and chromosome behaviour in meiosis in the genus Silene. This plant genus provides an opportunity to conduct a comparative cytogenetical study of the relatively early stages of sex chromosome evolution because it contains cytologically distinguishable heteromorphic sex chromosomes that have evolved relatively recently, 10-20 million years ago. We are using the cytogenetics tools we have developed for Arabidopsis to analyse the changes in sex chromosome structure and meiotic behaviour during sex chromosome evolution in Silene.
We are carrying out a high resolution comparative cytogenetic analysis of the X and Y chromosomes in dioecious Silene. In particular, we are investigating (i) How the structure of chromosomes have evolved to form clearly distinguishable heteromorphic X and Y chromosomes. (ii) How these plants cope with heterologous sex chromosomes during meiosis; specifically do they restrict pairing to the pseudoautosomal region (PAR) of the X and Y in plants? (iii) and what mechanisms are involved in suppressing recombination in the non-recombining regions (NRY) of the Silene Y chromosome? Overall, we would like to know if these mechanisms are similar to those arrived at in mammalian systems or alternatively, are we looking at novel approaches to achieve the same outcome.
Publications 2000 onwards...
PF Fransz, SJ Armstrong, J Hans de Jong, LD Parnell, C van Drunen, C Dean, P Zabel, T Bisseling, GH Jones. 2000. Integrated cytogenetic map of chromosome arm 45 of A. Thaliana: structural organization of heterochromatic knob and centromere region. Cell 100, 367-376.
SJ Armstrong, FCH Franklin, GH Jones. 2001. Nucleolus-associated telomere clustering precede meiotic chromosome synapsis in Arabidopsis thaliana. Journal of Cell Science 114, 4207-4217.
EC Howell, GC Barker, GH Jones, MJ Kearsey, GJ King, EP Kop, CD Ryder, GR Teakle, JG Vicente, SJ Armstrong. 2002. Integration of the cytogenetic and genetic linkage maps of Brassica oleracea. Genetics 161, 1225-1234.
SJ Armstrong, GH Jones. 2003. Meiotic cytology and chromosome behaviour in wild-type Arabidopsis thaliana. Journal of Experimental Botany 54, 1-10.
R Mercier, S J Armstrong, C Horlow, N P Jackson, CA Makaroff, D Vezon, G Pelletier, G H Jones, FCH Franklin. 2003. The meiotic protein SWI1 is required for axial element formation and recombination initiation in Arabidopsis thaliana. Development 130, 3309-3318.
SJ Armstrong, FCH Franklin, GH Jones. 2003. A meiotic time course for Arabidopsis thaliana. Sexual Plant Reproduction 16, 141-149.
JD Higgins*, SJ Armstrong*, FCH Franklin, GH Jones. 2004. The Arabidopsis MutS homologue At MSH4 functions at an early step in recombination; evidence for two classes of recombination in Arabidopsis. Genes and Development 18, 2557-2570 * joint first authors
EC Howell, SJ Armstrong, GC Barker, GH Jones, GJ King, CD Ryder, MJ Kearsey. 2005. Physical organization of the major duplication Brassica oleracea chromosome 06 revealed through fluorescence in situ hybridisation with Arabidopsis and Brassica probes. Genome 48, 1-11
N Jackson, E Sanchez-Moran, E Buckling, SJ Armstrong, GH Jones, FCH Franklin. 2006. Reduced crossovers and delayed prophase I progression an AtMLH3 deficient Arabidopsis. EMBO Journal, 25, 1315-1323.
C. Kerzendorfer ,J Vignard , A Pedrosa-Harand A, T Siwiec, S Akimcheva, S Jolivet, R Sablowski, SJ Armstrong, D Schweizer, R Mercier, P SchlÃ¶egelhofer. 2006. The Arabidopsis thaliana Meiotic Nuclear Division I (MNDI) homologue plays a key role in meiotic homologous recombination and synapsis. Journal of Cell Science, 119, 2486-2496.
J Vignard, T Siwiec, Lchelysheva, N Vrielynch, F Gonord, SJ Armstrong, P SchlÃ¶gelhofer, R Mercier 2007. The interplay of RecA-related proteins and the MND1-HOP2 complex during meiosis in Arabidopsis thaliana. . Plos Genet 3(10)
SJ Armstrong, D Filatov. 2008. A cytogenetic view of sex chromosome evolution in plants. Cytogenet. Genome Res, 120: 241-246.
RJ Scott, SJ Armstrong, J Doughty, M Spielman. 2008. Double Fertilization in Arabidopsis thaliana Involves a Polyspermy Block on the Egg but Not the Central Cell. Molecular Plant 1-9.
EC Howell, MJ Kearsey, GH Jones, GJ King, SJ Armstrong. 2008. A and C genome and chromosome identification in Brassica napus by sequential FISH and GISH. Genetics published ahead of print Oct 9 1534/genetics108.095895
DA Filatov, EC Howell, C Groutides, SJ Armstrong. 2009. Recent spread of a retrotransposon in the Silene latifolia genome apart from the Y chromosome. Genetics181, 811-817
NR Roberts, K Osman, SJ Armstrong. 2009. Telomere Distribution and Dynamics in Somatic and Meiotic Nuclei of Arabidopsis thaliana. Cytogenet. Genome Res. 124, 193-201
SJ Armstrong, E Sanchez- Moran, FCH Franklin. 2009. Cytological analysis of Arabidopsis thaliana meiotic chromosomes. Methods in Molecular Biology 558, Meiosis Volume 2 Cytological methods.
EC Howell, SJ Armstrong, DA Filatov. 2011. Dynamic gene order on the Silene latifolia Y chromosome. Chromosoma. 120, 287-295
K Osman, JD Higgins, E Sanchez-Moran, SJ Armstrong, FCH Franklin. 2011. Pathways to meiotic recombination in Arabidopsis thaliana. New phytologist 190, Issue 3, pages 523–544