PDF(Pubmed)
Abstract：
Although DNA methylation primarily represses TEs, it also represses select genes that are methylated in plant body tissues but demethylated by DNA glycosylases (DNGs) in endosperm or pollen. Activity of either one of two DNGs, MDR1 or DNG102, is essential for pollen viability in maize. Using single-pollen mRNA sequencing on pollen segregating mutations in both genes, we identified 58 candidate DNG target genes that account for 11.1% of the wild-type transcriptome but are silent or barely detectable in the plant body (sporophyte). They are unusual in their tendency to lack introns but even more so in their having TE-like methylation in their CDS. The majority have predicted functions in cell wall modification, and they likely support the rapid tip growth characteristic of pollen tubes. These results suggest a critical role for DNA methylation and demethylation in regulating maize genes with potential for extremely high expression in pollen but constitutive silencing elsewhere.
摘要：
尽管DNA甲基化主要抑制植物中的转座因子（TE），它还抑制选择胚乳和花粉基因。这些基因,或者它们的顺式调控元素，在植物身体组织中被甲基化，但在胚乳和花粉中被DNA糖基化酶（DNG）去甲基化，使他们的转录。两个DNG中的任何一个的活性，MDR1或DNG102对玉米的花粉活力至关重要。使用单花粉mRNA测序对两个基因的花粉分离突变，我们确定了58个候选DNG靶基因，其在双突变花粉中的表达强烈降低（平均降低124倍）。这些基因占野生型花粉多聚腺苷酸化转录组的11.1%，但是它们在植物体内是无声的或几乎无法检测到的。它们在缺乏内含子的倾向上是不寻常的，但在其编码DNA序列中具有TE样甲基化更是如此。此外，它们强烈富集了细胞壁修饰中的预测功能。虽然有些可能支持花粉粒细胞壁的发育，这组基因中的扩展蛋白酶和果胶酶表明细胞壁松动的功能，以支持花粉管的快速尖端生长特性，因为它们携带精子细胞通过雌蕊的母体质外体和细胞外基质。这些结果表明，DNA甲基化和去甲基化在调节玉米基因中具有关键作用，该基因在花粉中具有极高的表达潜力，但在其他地方具有组成性沉默。
