Synaptic responses to concerted genomic evolution in Lathyrus. I. Intergenomic effects
1993
Wallace, A.J. | Callow, R.S.
C(0) autotetraploids have been derived from seven diploid (x = 7) species of Lathyrus, varying in genome size (11-20 pg DNA/2C) and content of moderately repetitive DNA (5-12 pg/2C). Pairing patterns at metaphase-I in 942 pollen mother cells (PMCs), each with a minimum of 28 chiasmata, were compared with a model relating pairing autonomy to genomic organization. Autotetraploids of one species, L. aphaca, form on average one multivalent more than those of the other six (5.2 vs. 3.7-4.2/PMC). With the exception of L. aphaca, intergenomic differences in bivalent frequency and incidence of synaptic exchange correlate with the size of the genome, particularly that of the moderately repetitive component. Such nucleotypic correlations appear to reflect losses in numbers of autonomous synaptic sites, concomitant with concerted reductions in the size of the genome. They also indicate that autonomous synapsis may be governed by moderately repetitive sequences.
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