Sex-Specific Crossover Distributions and Variations in Interference Level along Arabidopsis thaliana Chromosome 4

Abstract

In many species, sex-related differences in crossover (CO) rates have been described at chromosomal and regional levels. In this study, we determined the CO distribution along the entire Arabidopsis thaliana Chromosome 4 (18 Mb) in male and female meiosis, using high density genetic maps built on large backcross populations (44 markers, >1,300 plants). We observed dramatic differences between male and female map lengths that were calculated as 88 cM and 52 cM, respectively. This difference is remarkably parallel to that between the total synaptonemal complex lengths measured in male and female meiocytes by immunolabeling of ZYP1 (a component of the synaptonemal complex). Moreover, CO landscapes were clearly different: in particular, at both ends of the map, male CO rates were higher (up to 4-fold the mean value), whereas female CO rates were equal or even below the chromosomal average. This unique material gave us the opportunity to perform a detailed analysis of CO interference on Chromosome 4 in male and female meiosis. The number of COs per chromosome and the distances between them clearly departs from randomness. Strikingly, the interference level (measured by coincidence) varied significantly along the chromosome in male meiosis and was correlated to the physical distance between COs. The significance of this finding on the relevance of current CO interference models is discussed.

Multilocus half-tetrad analysis and centromere mapping in citrus: evidence of SDR mechanism for 2n megagametophyte production and partial chiasma interference in mandarin cv ‘Fortune’

“…Interference values were estimated by three-point analysis for each arm of linkage group II, with results suggesting that it was higher for one arm (0.73) than for the other (0.53). Such variation of interference level between different parts of the genome has also been observed in Arabidopsis (Drouaud et al, 2007), in human (Lian et al, 2008) and in mouse (Broman et al, 2002).…”

Hot Regions of Noninterfering Crossovers Coexist with a Nonuniformly Interfering Pathway inArabidopsis thaliana

“…Studies in several plants and animals have shown that the average number of COs in meiosis may vary between male and female meiosis (see review by Lenormand and Dutheil 2005), but there is no general rule that governs the direction or degree of CO number variation. Similarly, the distribution of COs along chromosomes can also differ when comparing male and female meiosis (Drouaud et al 2007). Such distributions are generally nonuniform: some portions of the physical chromosome seem more likely to recombine while others hardly ever do (e.g., close to the centromere: Jones 1984; Anderson and Stack 2002).…”

“…Second, different interval sizes were pooled together to gain statistical power, introducing biases. It is thus worthwhile to see whether the modeling approach (based on fitting parameters of CO formation models rather than on measuring coefficients of coincidence) gives results similar to those of Drouaud et al (2007) while adding more insight. A first step in this direction was provided by Giraut et al (2011) using the single pathway gamma model.…”

“…Similarly, the distribution of COs along chromosomes can also differ when comparing male and female meiosis (Drouaud et al 2007). Such distributions are generally nonuniform: some portions of the physical chromosome seem more likely to recombine while others hardly ever do (e.g., close to the centromere : Jones 1984;Anderson and Stack 2002).…”

“…As a first answer to these questions, previous work on Arabidopsis male chromosome 4 (Drouaud et al 2007) found that both the local recombination rates and the synaptonemal complex lengths were significantly different when comparing male and female meiosis. Furthermore, those authors concluded that interference strength varied along the length of chromosome 4 through tests using the classical coefficient of coincidence (Ott 1999).…”