研究人员使用单个花粉前体的等位基因特异性RNA测序来跟踪了玉米花粉中向单倍体表达的转变。研究人员观察到减数分裂后11天内广泛的双亲表达，表明由二倍体孢子体合成的转录本长期存在于单倍体阶段。随后，在花粉有丝分裂I期，在单倍体基因组活跃的新转录驱动下，迅速和全面地转换为单倍体表达。如果基因在花粉有丝分裂I之后（而不是之前）表达，则显示出纯化选择的增加。这项工作确定了花粉中单倍体选择可能发挥作用的时间。
据了解，开花植物在多细胞的单倍体（配子体）和二倍体（孢子体）之间交替。花粉积极转录其单倍体基因组，甚至在单一植物的花粉粒之间提供表型多样性。
附：英文原文
Title: Gametophyte genome activation occurs at pollen mitosis I in maize
Author: Brad Nelms, Virginia Walbot
Issue&Volume: 2022-01-28
Abstract: 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.
DOI: abl7392
Source: https://www.science.org/doi/10.1126/science.abl7392