Tomato (Lycopersicon esculentum) synaptonemal complex karyotype

A karyotype and an idiogram of tomato synaptonemal complexes (SCs) are presented in Table I and Figure 1, respectively. The karyotype and idiogram are based on an analysis of 100 spreads of SCs that were prepared essentially as described by Stack (1982). The SCs are distinguished by relative length, arm ratio, and percent heterochromatin in each arm. Each SC was related to a specific chromosome by observing SC spreads of trisomics for all twelve chromosomes. In reference to all the above characteristics, SC are similar to their corresponding pachytene bivalents in squash preparations (Romanna and Prakken, 1967). This work is a necessary prerequisite for producing a physical map of recombination on SCs. The map will be based on the distribution of recombination nodules (RNs) on SCs (RNs are thought to lie at sites of crossing over - Carpenter, 1975). This work was supported in part by grants DCB-8718170 and DCB-8918613 from NSF and grant 1878-670 from the Colorado Agricultural Experiment Station.

Literature cited:

Carpenter, A. 1975. Proc. Nat. Acad. Sci. (USA) 72:3186-3189.

Romanna, M. and R. Prakken. 1967. Genetica 38:115-133.

Stack, S. 1983. Stain Technol. 57:265-272.

Table 1. Tomato SC karyotype.

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SC#  Relative     Arm ratio    Percent heterochromatin
                              ________________________
     length (%)  (long/short) long     short    total 
______________________________________________________
1       13           3.0       21       47       28  
2       11           5.5*      22       100      36  
3       10           3.3       23       42       31  
4        9           2.5       35       38       36  
5        7           1.0       43       42       43  
6        8           3.3       25       36       27  
7        8           1.8       34       36       35  
8        8           2.2       30       39       33  
9        7           1.7       43       37       41  
10       7           2.0       42       50       45  
11       7           1.2       45       21       33  
12       6           1.1       50       50       50  
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Figure 1. Idiogram of tomato synaptonemal complexes. The twelve SCs are shown as line drawings. The thick lines represent euchromatin, the thin lines represent heterochromatin, and the circles represent kinetochores. SCs are numbered in order from left to right. The bar is equal to 10 m.