Inter- and intra-plant SC length variation in Crepis capillaris

Abstract

Synaptonemal complexes (SCs) were measured in large samples (16-31) of pachytene nuclei from five different plants of Crepis capillaris, with the aim of conducting a systematic study of intra-plant and interplant SC length variation. Individual plants showed considerable variation in SC length among cells (average range= 1.83x), which is presumed to reflect stage-related differences in chromosome and SC length during pachytene. The five plants selected for study showed highly significant differences in SC length. These differences are interpreted as real differences in the means and ranges of SC lengths in different genotypes rather than, for example, sampling effects. Mean SC lengths at pachytene and mean chiasma frequencies at metaphase I show signs of being positively related, but the correlation is statistically non-significant, indicating a need for more extensive study.

Variable patterns of chromosome synapsis at pachytene in Hordeum vulgarexH. bulbosum hybrids and their parents

“…Our results suggest that there are genotypic effects on pairing and recombination in these Hordeum hybrids, as has been found in several other grass species hybrid combinations (DOVER and RILEY 1972;EVANS and AUNG 1985). A positive relationship between SC length and chiasma/recombination frequency has been reported previously in many species (BOJKO 1983(BOJKO , 1985JONES and CROFT 1989;DE AZKUE and JONES 1993;QUEVEDO et al 1997). The hybrids used in the present study, 102C2 and 103K5, have been shown to have mean recombination frequencies of 0.53 and 0.33 per pollen mother cell, respectively (ZHANG et al 1999) and now, a 32 % difference in SC length.…”

“…The present study shows an almost two‐fold variation in SC length between the two parental species, H. vulgare and H. bulbosum , and also between the two different interspecific hybrid combinations. It is possible that part of this variation may be due to sampling cells at different stages of pachytene, however, the relationship between pachytene stage and SC length is not clear‐cut and there is no uniform pattern of reduction in length in later pachytene stages (M oses et al 1977; A nderson et al 1985; D e A zkue and J ones 1993). In Hordeum , as in several other plant groups, it is not possible to identify the sub‐stages of pachytene but as our measurements were made on cells prepared from many florets on several occasions they represent a reasonable sample of any intraspecific variation.…”

“…The analysis of chromosome behaviour at pachytene has been greatly facilitated by the development of synaptonemal complex (SC) spreading techniques (A lbini et al 1984) that allow the extent of chromosome synapsis to be measured and compared between different plants. Variation in SC length is widely reported to be correlated with recombination frequency in a variety of plant and animal species (J ones and C roft 1989; D e A zkue and J ones 1993; Q uevedo et al 1997). It is also possible to use the frequency of late recombination nodules (RNs) associated with the SC to measure recombination frequencies since the number and location of these nodules corresponds closely with the number and position of chiasmata in a wide variety of species (C arpenter 1975; S tack and A nderson 1986; S tack and R oelofs 1996).…”

Correlated variation of chiasma frequency and synaptonemal complex length in Locusta migratoria

“…In all these cases, whatever the cause, higher chiasma/crossover frequencies are associated with longer SCs. An indication of the same relationship was found in wild population plants of Crepis capillaris, which was not dependent on sex difference or the presence of additional heterochromatin (de Azkue & Jones, 1993), but this conclusion was very tentative because of the low number of plants included in the study. It therefore remains a priority to determine whether this relationship does obtain in 'normal' individuals, independently of any special effects such as sex difference or possession of heterochromatin.…”