Meiosis in autopolyploid Crepis capillaris. III. Comparison of triploids and tetraploids; evidence for non independence of autonomous pairing sites

Abstract

A comparison of meiotic pairing patterns in autopolyploids of Crepis capi/laris reveals that the chromosomes of autotriploids form 60 per cent more pairing partner switches (PPSs) than autotetraploids. This difference is highly significant and affects all three chromosomes of Crepis capillaris to about the same extent. However, from theoretical considerations, the chromosomes of autotriploids and autotetraploids are expected to form equal numbers of PPSs provided that they have the same numbers of autonomous pairing sites (APSs) which are acting independently or showing the same degree of dependence and there are no pairing preference differences.Differences in numbers of APSs or in pairing preferences are thought to be unlikely and therefore it is considered that the difference in PPS frequencies reflects some form of interference between APSs affecting the choice of pairing partners but to different degrees in triploids and tetraploids. Such interdependence is fully consistent with the original concept of APSs as 'regions with the capacity to initiate pairing partner exchange in an autopolyploid, regardless of the likelihood of such exchange'.

What makes homologous chromosomes find each other in meiosis? A review and an hypothesis

“…In triploids and higher uneven polyploids the numbers of multivalents are greater than in the corresponding tetraploids, as is the number of partner switches, although theoretically they should be the same (Mather 1939;Loidl 1986;Loidl and Jones 1986;Loidl et al 1990;Vincent and Jones 1993;Jones 1994). Apparently, in triploids, after all three chromosomes have initially attracted each other mutually and two have synapsed at one site, one is left alone, but where no SC has yet formed all three continue to attract each other.…”

“…Apparently, in triploids, after all three chromosomes have initially attracted each other mutually and two have synapsed at one site, one is left alone, but where no SC has yet formed all three continue to attract each other. A chromosome that is unsynapsed when the other two have synapsed, remains in close proximity and has a good chance to pair with one of the other two where these fail to synapse (Jones 1994). Close alignment between the third chromosome and a synapsed pair has been observed in numerous cases.…”

Evolution in an autopolyploid group displaying predominantly bivalent pairing at meiosis: genomic similarity of diploid Vaccinium darrowi and Autotetraploid V. corymbosum (Ericaceae)

“…Blueberry is apparently not unusual in this regard as predominantly bivalent pairing at diakinesis and metaphase I has been observed in a number of artificial and naturally occurring autotetraploid species (Soltis and Rieseberg, 1986;Crawford and Smith, 1984;Samuel, Pinsker, and Ehrendorfer, 1990;Jones, 1994). Blueberry is apparently not unusual in this regard as predominantly bivalent pairing at diakinesis and metaphase I has been observed in a number of artificial and naturally occurring autotetraploid species (Soltis and Rieseberg, 1986;Crawford and Smith, 1984;Samuel, Pinsker, and Ehrendorfer, 1990;Jones, 1994).…”

Meiosis and Its Deviations in Polyploid Plants

“…These synaptic multivalents occur in both allo-and autopolyploid plants ( fig. 2 B, C) with partner switches occurring more frequently in triploids than in tetraploids [Loidl, 1986;Loidl and Jones, 1986;Jones, 1994]. In wheat, several studies have highlighted the presence of synaptic multivalents at mid-zygotene with a mean number of 12 lateral elements involved in multivalent associations in hexaploid wheat [Holboth, 1981;Holm, 1986;Martinez et al, 2001a, b].…”