State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for Genetics and Development, School of Life Sciences, Fudan University, Shanghai 200438, China.
J Integr Plant Biol. 2017 Sep;59(9):657-668. doi: 10.1111/jipb.12573.
Both female and male gametophytes harbor companion cells and gametes. MET1, a DNA methyltransferase, is down-regulated in companion cells. However, how MET1 is differentially regulated in gametophytes remains unexplored. ARID1, a transcription factor that is specifically depleted in sperm cells, is occupied by MET1-dependent CG methylation. Here, we show that MET1 confines ARID1 to the vegetative cell of male gametes, but ARID1 conversely represses MET1 in the central cell of female gametes. Compared to the vegetative cell-localization in wild type pollen, ARID1 expands to sperm cells in the met1 mutant. To understand whether MET1-dependent ARID1 inhibition exists during female gametogenesis, we first show that ARID1 is expressed in the megaspore mother cell (MMC), ARID1 but not MET1 is detectable in the central cell at maturity. Interestingly, compared to the absence of MET1 in the central cell and the egg cell of wild type ovules, MET1 significantly accumulates in these two cells in arid1 ovules. Lastly, we show that both ARID1 and MET1 are required for the cell specification of MMC. Collectively, our results uncover a reciprocal dependence between ARID1 and MET1, and provide a clue to further understand how the specification of MMC is likely regulated by DNA methylation.
雌雄配子体都含有伴胞和配子。MET1 是一种 DNA 甲基转移酶，在伴胞中下调。然而，MET1 在配子体中是如何被差异调控的仍未被探索。ARID1 是一种特异性耗尽精子细胞中的转录因子，被 MET1 依赖的 CG 甲基化占据。在这里，我们表明 MET1 将 ARID1 局限于雄性配子体的营养细胞中，但 ARID1 反过来在雌性配子体的中央细胞中抑制 MET1。与野生型花粉中营养细胞定位相比，ARID1 在 met1 突变体中扩展到精子细胞。为了了解 MET1 依赖性 ARID1 抑制是否存在于雌性配子发生过程中，我们首先表明 ARID1 在大孢子母细胞（MMC）中表达，在成熟时中央细胞中可检测到 ARID1，但不能检测到 MET1。有趣的是，与野生型胚珠中中央细胞和卵细胞中没有 MET1 相比，arid1 胚珠中这两个细胞中 MET1 明显积累。最后，我们表明 ARID1 和 MET1 都需要 MMC 的细胞特化。总之，我们的结果揭示了 ARID1 和 MET1 之间的相互依赖关系，并为进一步了解 MMC 的特化可能如何受到 DNA 甲基化的调控提供了线索。
