John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK.
Agroforestry and Plant Biochemistry, Proteomics and Systems Biology, Department of Biochemistry and Molecular Biology, University of Cordoba, Cordoba, Spain.
Theor Appl Genet. 2020 Mar;133(3):809-828. doi: 10.1007/s00122-019-03508-9. Epub 2019 Dec 18.
The 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. We initially assessed the effects of low temperature 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 temperature in a controlled environment room 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 7 days at 13 °C, suggesting that Ltp1 is deleted in this mutant. Immunolocalisation of the meiotic proteins ASY1 and ZYP1 on ltp1 mutants showed that low temperature results in a failure to complete synapsis at pachytene. KASP genotyping revealed that the ltp1 mutant 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 temperatures is the meiotic recombination gene Dmc1. The ltp1 mutants were subsequently treated at 30 °C for 24 h during meiosis and exhibited a reduced number of crossovers and increased univalence, though to a lesser extent than at 13 °C. We therefore renamed our ltp1 mutant 'ttmei1' (temperature-tolerant meiosis 1) to reflect this additional loss of high temperature tolerance.
小麦 5D 染色体上的减数分裂重组基因 Dmc1 被鉴定为维持正常染色体联会和交叉的候选基因，无论是在低温还是可能的高温下。我们最初评估了低温对六倍体小麦（Triticum aestivum L.）品种‘Chinese Spring’减数分裂染色体联会和交叉形成的影响。在低温下，以前在缺乏 5D 染色体长臂（5DL）的 Chinese Spring 系中观察到了联会和染色体单价，这导致了 5DL 携带一个基因（Ltp1）的假设，该基因在低温下稳定小麦染色体配对。在本研究中，Chinese Spring 野生型和 5DL 染色体间缺失突变体植物在受控环境室中经历了从减数分裂前期到早期减数分裂 I 的低温暴露。鉴定出一个 5DL 缺失突变体，其减数分裂染色体在 13°C 下 7 天后的中期 I 表现出极高的联会和染色体单价水平，表明该突变体中缺失了 Ltp1。在 ltp1 突变体上进行的减数分裂蛋白 ASY1 和 ZYP1 的免疫定位显示，低温导致在粗线期无法完成联会。KASP 基因分型表明，ltp1 突变体在 5DL 中缺失了 4 Mb。在该缺失区域内的 41 个基因中，低温下稳定染色体配对的最强候选基因是减数分裂重组基因 Dmc1。随后，ltp1 突变体在减数分裂期间在 30°C 下处理 24 小时，表现出交叉减少和单价增加，尽管程度低于 13°C。因此，我们将我们的 ltp1 突变体重新命名为“ttmei1”（耐温减数分裂 1），以反映这种高温耐受性的额外丧失。
