HAUBER, DONALD P. Dept. of Biological Sciences, Loyola University, New Orleans, LA 70118. - Synaptonemal complex formation in diploid Tradescantia ohiensis.
The synaptonemal complex (SC) is the linear, tripartite structure that
is believed to play a critical role in the orientation of homologous
chromosomes during synapsis in prophase I. Over the past 25 years, a
whole-mount spreading procedure has been used that allows for detailed
examination of intact SCs. A follow-up to a study performed by
Hansenkampf and colleagues (1984a,b, 1985) on Tradescantia
ohiensis was recently performed using a modified SC spreading
technique. The modified technique, which calls for desalted sulfatase
enzyme in the bursting medium to break down the pollen mother cell
walls, produced several nearly completely synapsed, whole pachytene
spreads. The earlier studies had little success in obtaining pachytene
SC spreads and mainly focused on spreads in zygotene in which synapsis
was never complete. This current study demonstrates that synapsis in
Tradescantia does progress nearly to completion. It agrees with
the previous reports in that synapsis appears to initiate at the
telomeres. Also, the average total SC length from the present study
(1092±89.97 µm) was comparable to the
average obtained in the 1985 study (1246±160.3 µm). The current study also revealed for
the first time, the "bouquet" arrangement of the pachytene
SCs, which is often observed in cases where synapsis initiates at the
telomeres, and has been reported for Rhoeo, another
commelinaceous species.
Key words: chromosomes, cytogenetics, meiosis, synapsis, synaptonemal complex, Tradescantia