Four effects of elevated temperature on chiasma formation in the locust Schistocerca gregaria

Abstract

Using an inbred stock of Schistocerca gregaria in which inter-individual variation was reduced, the effects of high temperature treatments on male meiosis have been investigated. These experiments involved both heat-treatments of relatively short duration, ranging from 1-6 days at 40°C followed by a return to 30°C, and longer periods of time at a constant 40°C. It was found that four effects on chiasma frequency could be produced. In addition to the major reduction in chiasma frequency reported earlier, a second small period of reduction was obtained. The other two effects involved increases in chiasma frequency. Three of these effects, the two decreases and one increase, were produced following heat-treatments of meiotic prophase stages, after premeiotic DNA synthesis was completed. The other increase was obtained following heat-treatment of spermatogonia. The possible nature of these effects is discussed. It is suggested that the late prophase period, during which a small increase in chiasma frequency (called Effect 1) is produced by heat-treatments, could correspond to at least part of the time during which chiasmata form.

Ethyl Methane Sulphonate (EMS) Induced (Partial) Asynaptic Mutant in Faba Bean (Vicia faba L.)

“…Loidl (1989) described the reduction in the meiotic chromosome pairing and reduced number of chiasmata after exposing Allium ursinum to elevated temperatures and explained that these were due to i) failure of homologous recognition, ii) accumulation of additional material between pairing axes (which also affects completed SCs), and iii) aggregation of large numbers of non-homologous axes. Henderson (1988) in grasshopper Schistocerca observed heat increased chiasma frequency if administered at the spermatogonial stage and late zygotene/early pachytene stage. In some plants also, rise in temperature was found to be associated with rise in the chiasma frequency e.g.…”

Interactions between heat-induced chiasma frequency changes in Schistocerca gregaria

“…The control chiasma frequency levels of individuals maintained at a constant 30°C have been described in the previous publication of the present series (Henderson, 1988) and will not be repeated here. EXPERIMENTAL …”

“…The inbred stocks of S. gregaria used were those described in an earlier publication in this series (Henderson, 1988). The experimental procedure was also similar to that used before.…”

“…The four effects of short heat-treatments on chiasma frequency at male meiosis in locusts have been numbered, for simplicity, Effects 1-4 (Henderson, 1970;1988). They are: Effect 1.…”

“…Using the locusts Schistocerca gregaria and Locusta migratorici it has been found that as many as four effects can be obtained, two increases and two decreases, when early meiotic, or premeiotic, stages are heat-treated at 40°C (Henderson, 1970;1988;Buss, 1971). They are most readily demonstrated if relatively short heat-treatments of 2-6 days are given, followed by incubation at a lower control temperature.…”