Dmc1is a candidate for temperature tolerance during wheat meiosis

Abstract

Key messageThe meiotic recombination gene Dmc1 on wheat chromosome 5D has been identified as a candidate for the maintenance of normal chromosome synapsis and crossover at low and possibly high temperatures. AbstractWe have assessed the effects of high and low temperatures on meiotic chromosome synapsis and crossover formation in the hexaploid wheat (Triticum aestivum L.) variety 'Chinese Spring'. At low temperatures, asynapsis and chromosome univalence have been observed before in Chinese Spring lines lacking the long arm of chromosome 5D (5DL), which led to the proposal that 5DL carries a gene (Ltp1) that stabilises wheat chromosome pairing at low temperatures. In the current study, Chinese Spring wild type and 5DL interstitial deletion mutant plants were exposed to low (13°C) or high (30°C) temperatures in controlled environment rooms during a period from premeiotic interphase to early meiosis I. A 5DL deletion mutant was identified whose meiotic chromosomes exhibit extremely high levels of asynapsis and chromosome univalence at metaphase I after seven days at 13°C. This suggests that the mutant, which we name ttmei1 (temperature tolerance in meiosis 1) has a deletion of a gene that, like Ltp1, normally stabilises chromosome pairing at low temperatures. Immunolocalisation of the meiotic proteins ASY1 and ZYP1 on ttmei1 mutants showed that low temperature results in a failure to complete synapsis at pachytene. After 24 hours at 30°C, ttmei1 mutants exhibited a reduced number of crossovers and increased univalence, but to a lesser extent than at 13°C. KASP genotyping revealed that ttmei1 has a 4 Mb deletion in 5DL. Of 41 genes within this deletion region, the strongest candidate for the stabilisation of chromosome pairing at low (and possibly high) temperatures is the meiotic recombination gene Dmc1. KeywordsWheat, high temperature, low temperature, meiosis, chromosome crossover, Dmc1Author contribution statement TD generated the gamma deletion lines, phenotyped the Chinese Spring lines at high and low temperature and identified the ttmei1 deletion mutant. TD and AP carried out the KASP genotyping.M-DR scored chromosome crossover and performed the statistical analysis. AM carried out the immunolocalisation experiments and produced the immunolocalisation figure. AKA identified putative meiosis-specific genes in the 4 Mb deleted region of ttmei1, carried out the sequence 3 alignments and produced the gene expression figures; TD produced all other figures and wrote the manuscript. PS provided a critique of the approach and contributed to discussion of the results. GM provided the concept, provided thoughts and guidance and revised and edited the manuscript. Conflict of interestThe authors declare that they have no conflict of interest. 5DL-9 and 5DL-13 (Endo and Gill 1996). DNA extractionsPlants were initially grown in modular trays in a controlled environment room (CER) at 20°C (day) and 15°C (night) with a 16-hour photoperiod (lights on between 10:00 and 02:00) and 70 % humidity.Wheat seedlings were grown to the ...

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