Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge CB2 3EA, UK.
Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK.
Curr Biol. 2019 Aug 19;29(16):2676-2686.e3. doi: 10.1016/j.cub.2019.06.084. Epub 2019 Aug 1.
Meiotic crossover frequency varies within genomes, which influences genetic diversity and adaptation. In turn, genetic variation within populations can act to modify crossover frequency in cis and trans. To identify genetic variation that controls meiotic crossover frequency, we screened Arabidopsis accessions using fluorescent recombination reporters. We mapped a genetic modifier of crossover frequency in Col × Bur populations of Arabidopsis to a premature stop codon within TBP-ASSOCIATED FACTOR 4b (TAF4b), which encodes a subunit of the RNA polymerase II general transcription factor TFIID. The Arabidopsis taf4b mutation is a rare variant found in the British Isles, originating in South-West Ireland. Using genetics, genomics, and immunocytology, we demonstrate a genome-wide decrease in taf4b crossovers, with strongest reduction in the sub-telomeric regions. Using RNA sequencing (RNA-seq) from purified meiocytes, we show that TAF4b expression is meiocyte enriched, whereas its paralog TAF4 is broadly expressed. Consistent with the role of TFIID in promoting gene expression, RNA-seq of wild-type and taf4b meiocytes identified widespread transcriptional changes, including in genes that regulate the meiotic cell cycle and recombination. Therefore, TAF4b duplication is associated with acquisition of meiocyte-specific expression and promotion of germline transcription, which act directly or indirectly to elevate crossovers. This identifies a novel mode of meiotic recombination control via a general transcription factor.
减数分裂交叉频率在基因组内存在差异，这会影响遗传多样性和适应性。反过来，种群内的遗传变异可以在顺式和反式中改变交叉频率。为了确定控制减数分裂交叉频率的遗传变异，我们使用荧光重组报告基因筛选了拟南芥品系。我们将拟南芥 Col 与 Bur 群体中的交叉频率遗传修饰因子定位到 TBP 相关因子 4b (TAF4b) 内的一个提前终止密码子，TAF4b 编码 RNA 聚合酶 II 通用转录因子 TFIID 的一个亚基。拟南芥 taf4b 突变是在不列颠群岛发现的一种罕见变体，起源于爱尔兰西南部。我们利用遗传学、基因组学和免疫细胞化学，证明了 taf4b 交叉的全基因组减少，在亚端粒区域减少最为明显。我们从纯化的减数分裂细胞中进行 RNA 测序 (RNA-seq)，结果表明 TAF4b 在减数分裂细胞中表达丰富，而其同源物 TAF4 则广泛表达。与 TFIID 在促进基因表达中的作用一致，野生型和 taf4b 减数分裂细胞的 RNA-seq 鉴定出广泛的转录变化，包括调节减数分裂细胞周期和重组的基因。因此，TAF4b 复制与获得减数分裂细胞特异性表达和促进生殖细胞转录有关，这直接或间接提高了交叉频率。这确定了一种通过通用转录因子控制减数分裂重组的新方式。
