Inversions of chromosome arms 4AL and 2BS in wheat invert the patterns of chiasma distribution
In many species, including wheat, crossing over is distal, and the proximal regions of chromosome arms contribute little to genetic maps. This was thought to be a consequence of terminal initiation of synapsis favoring distal crossing over. However, in an inverted rye chromosome arm, the pattern of metaphase I chiasmata was also inverted, suggesting that crossover frequencies were specific to chromosome segments. Here, wheat chromosome arms 2BS and 4AL, with essentially entire arms inverted in reverse tandem duplications (rtd), were studied in the MI of meiosis. Inversion–duplication placed the recombining segments in the middle of the arms. While the overall pairing frequencies of the inverted–duplicated arms were considerably reduced relative to normal arms, chiasmata, if present, were always located in the same regions as in structurally normal arms, and relative chiasma frequencies remained the same. The frequencies of fragment or fragment + bridge configurations in AI and AII indicated that of the two tandemly arranged copies of segments in rtds, the more distal inverted segments were more likely to cross over than the segments in their original orientations. These observations show that also in wheat, relative crossover frequencies along chromosome arms are predetermined and independent of the segment location. The segments normally not licensed to cross over do not do so even when placed in seemingly most favorable positions for it.
KeywordsNormal Chromosome Crossover Frequency Inverted Segment Chiasma Distribution Telomere Bouquet
DK was supported by the Ministry of Education, Youth and Sports of the Czech Republic and the European Regional Development Fund (Operational Programme Research and Development for Innovations No. CZ.1.05/2.1.00/01.0007). GL was supported by the Hungarian National Research Fund (K67808) and the Js Bolyai Research Scholarship of the Hungarian Academy of Sciences.
- Close TJ, Bhat PR, Lonardi S, Wu Y, Rostoks N, Ramsay L, Druka A, Stein N, Svensson JT, Wanamaker S, Bozdag S, Roose ML, Moscou MJ, Chao S, Varshney RK, Szűcs P, Sato K, Hayes PM, Matthews DE, Kleinhofs A, Muehlbauer GJ, DeYoung J, Marshall DF, Madishetty K, Fenton RD, Condamine P, Graner A, Waugh R (2009) Development and implementation of high-throughput SNP genotyping in barley. BMC Genomics 10:582–595PubMedCrossRefGoogle Scholar
- Fussel CP (1987) The Rabl orientation: a prelude to synapsis. In: Moens PB (ed) Meiosis. Academic Press, Orlando, pp 275–299Google Scholar
- Lukaszewski AJ (2003) Manipulation of recombination in wheat. In: Pogna NE et al. (eds) Proc. 10th Int. Wheat Genet Symp. Paestum, Italy, Sept 2003, pp.73-76Google Scholar
- Luo MC, Deal KR, Akhunova ED, Akhunova AR, Anderson OD, Anderson JA, Blake N, Clegg MT, Coleman-Derr D, Conley EJ, Crossman CC, Dubcovsky J, Gill BS, Gub YQ, Hadam J, Heo HY, Huo N, Lazo G, Ma Y, Matthews DE, McGuire PE, Morrell PL, Qualset CO, Renfro J, Tabanao D, Talbert LE, Tiana C, Toleno DM, Warburton ML, Youb FM, Zhang W, Dvorak J (2009) Genome comparisons reveal a dominant mechanism of chromosome number reduction in grasses and accelerated genome evolution in Triticeae. Proc Natl Acad Sci USA 106:15780–15785PubMedCrossRefGoogle Scholar
- Mayer KFX, Martis M, Hedley PE, Simkova H, Liu H, Morris JA, Steuernagel B, Taudien S, Roessner S, Gundlach H, Kubalakova M, Suchankova P, Murat F, Felder M, Nussbaumer T, Graner A, Salse J, Endo T, Sakai H, Tanaka T, Itoh T, Sato K, Platzer M, Matsumoto M, Scholz U, Dolezel J, Waugh R, Stein N (2011) Unlocking the barley genome by chromosomal and comparative genomics. Plant Cell 23:1249–1263PubMedCrossRefGoogle Scholar
- Sallee PJ, Kimber G (1978) An analysis of the pairing of wheat telocentric chromosomes. In: Ramanujan S (ed) Proc. 5th Int. Wheat Genet. Symp. New Dehli, India, pp. 408–419Google Scholar