Gametophyte genome activation occurs at pollen mitosis I in maize
Gametophyte genome activation occurs at pollen mitosis I in maize
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DOI：
10.1126/science.abl7392
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发表时间：
2022-01-28
期刊：
影响因子：
56.9
通讯作者：
Walbot, Virginia
中科院分区：
文献类型：
--
作者：
Nelms, Brad;Walbot, Virginia
开花植物在多细胞单倍体（配子体）和二倍体（孢子体）世代之间交替。花粉活跃地转录其单倍体基因组，甚至在来自单个植物的花粉粒之间提供表型多样性。在这项研究中，我们使用等位基因特异性RNA测序的单个花粉前体，以跟踪在玉米花粉中的单倍体表达的转变。我们观察到广泛的双等位基因表达11天后减数分裂，表明转录合成的二倍体孢子体持续长到单倍体阶段。随后，在花粉有丝分裂I中，由来自单倍体基因组的活跃的新转录驱动，有一个快速和全球性的向单等位基因表达的转化。如果基因在花粉有丝分裂I之后（而不是之前）表达，则表明纯化选择增加的证据。这项工作确立了单倍体选择在花粉中起作用的时间。
Flowering plants alternate between multicellular haploid (gametophyte) and diploid (sporophyte) generations. Pollen actively transcribes its haploid genome, providing phenotypic diversity even among pollen grains from a single plant. In this study, we used allele-specific RNA sequencing of single pollen precursors to follow the shift to haploid expression in maize pollen. We observed widespread biallelic expression for 11 days after meiosis, indicating that transcripts synthesized by the diploid sporophyte persist long into the haploid phase. Subsequently, there was a rapid and global conversion to monoallelic expression at pollen mitosis I, driven by active new transcription from the haploid genome. Genes showed evidence of increased purifying selection if they were expressed after (but not before) pollen mitosis I. This work establishes the timing during which haploid selection may act in pollen.