National Maize Improvement Centre of China, China Agricultural University, Beijing, 100193, China.
Beijing Key Laboratory of New Technique in Agricultural Application, College of Plant Science and Technology, Beijing University of Agriculture, Beijing, 102206, China.
New Phytol. 2017 Sep;215(4):1503-1515. doi: 10.1111/nph.14688. Epub 2017 Jul 19.
A major resistance quantitative trait locus, qRfg1, significantly enhances maize resistance to Gibberella stalk rot, a devastating disease caused by Fusarium graminearum. However, the underlying molecular mechanism remains unknown. We adopted a map-based cloning approach to identify the resistance gene at qRfg1 and examined the dynamic epigenetic changes during qRfg1-mediated maize resistance to the disease. A CCT domain-containing gene, ZmCCT, is the causal gene at the qRfg1 locus and a polymorphic CACTA-like transposable element (TE1) c. 2.4 kb upstream of ZmCCT is the genetic determinant of allelic variation. The non-TE1 ZmCCT allele is in a poised state, with predictive bivalent chromatin enriched for both repressive (H3K27me3/H3K9me3) and active (H3K4me3) histone marks. Upon pathogen challenge, this non-TE1 ZmCCT allele was promptly induced by a rapid yet transient reduction in H3K27me3/H3K9me3 and a progressive decrease in H3K4me3, leading to disease resistance. However, TE1 insertion in ZmCCT caused selective depletion of H3K4me3 and enrichment of methylated GC to suppress the pathogen-induced ZmCCT expression, resulting in disease susceptibility. Moreover, ZmCCT-mediated resistance to Gibberella stalk rot is not affected by photoperiod sensitivity. This chromatin-based regulatory mechanism enables ZmCCT to be more precise and timely in defense against F. graminearum infection.
一个主要的抗性数量性状位点 qRfg1 显著增强了玉米对禾谷镰刀菌引起的毁灭性病害——玉米茎腐病的抗性。然而，其潜在的分子机制尚不清楚。我们采用基于图谱的克隆方法来鉴定 qRfg1 上的抗性基因，并研究了 qRfg1 介导的玉米对该病害抗性过程中的动态表观遗传变化。一个 CCT 结构域包含基因 ZmCCT 是 qRfg1 位点的候选基因，ZmCCT 上游约 2.4kb 的 CACTA 样转座元件（TE1）是等位变异的遗传决定因素。非 TE1 的 ZmCCT 等位基因处于一种启动状态，具有预测的双价染色质，富含抑制性（H3K27me3/H3K9me3）和活性（H3K4me3）组蛋白标记。在病原体攻击下，非 TE1 的 ZmCCT 等位基因通过快速但短暂的 H3K27me3/H3K9me3 减少和 H3K4me3 的逐渐减少而被迅速诱导，从而导致抗性。然而，TE1 在 ZmCCT 中的插入导致 H3K4me3 的选择性耗竭和甲基化 GC 的富集，从而抑制了病原体诱导的 ZmCCT 表达，导致易感性。此外，ZmCCT 介导的对禾谷镰刀菌茎腐病的抗性不受光周期敏感性的影响。这种基于染色质的调控机制使 ZmCCT 在防御禾谷镰刀菌感染方面更加精确和及时。
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