Horticulture Department, University of Wisconsin, Madison, WI, 53706, USA.
Department of Plant Science, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China.
Theor Appl Genet. 2018 Jul;131(7):1577-1587. doi: 10.1007/s00122-018-3099-1. Epub 2018 Apr 21.
Map-based cloning identified a candidate gene for resistance to the anthracnose fungal pathogen Colletotrichum orbiculare in cucumber, which reveals a novel function for the highly conserved STAYGREEN family genes for host disease resistance in plants. Colletotrichum orbiculare is a hemibiotrophic fungal pathogen that causes anthracnose disease in cucumber and other cucurbit crops. No host resistance genes against the anthracnose pathogens have been cloned in crop plants. Here, we reported fine mapping and cloning of a resistance gene to the race 1 anthracnose pathogen in cucumber inbred lines Gy14 and WI 2757. Phenotypic and QTL analysis in multiple populations revealed that a single recessive gene, cla, was underlying anthracnose resistance in both lines, but WI2757 carried an additional minor-effect QTL. Fine mapping using 150 Gy14 × 9930 recombinant inbred lines and 1043 F individuals delimited the cla locus into a 32 kb region in cucumber Chromosome 5 with three predicted genes. Multiple lines of evidence suggested that the cucumber STAYGREEN (CsSGR) gene is a candidate for the anthracnose resistance locus. A single nucleotide mutation in the third exon of CsSGR resulted in the substitution of Glutamine in 9930 to Arginine in Gy14 in CsSGR protein which seems responsible for the differential anthracnose inoculation responses between Gy14 and 9930. Quantitative real-time PCR analysis indicated that CsSGR was significantly upregulated upon anthracnose pathogen inoculation in the susceptible 9930, while its expression was much lower in the resistant Gy14. Investigation of allelic diversities in natural cucumber populations revealed that the resistance allele in almost all improved cultivars or breeding lines of the U.S. origin was derived from PI 197087. This work reveals an unknown function for the highly conserved STAYGREEN (SGR) family genes for host disease resistance in plants.
基于图谱的克隆鉴定了黄瓜对炭疽病真菌病原体炭疽菌的抗性候选基因，这揭示了高度保守的 STAYGREEN 家族基因在植物宿主抗病性中的新功能。炭疽菌是一种半活体真菌病原体，可引起黄瓜和其他葫芦科作物的炭疽病。在作物植物中尚未克隆出针对炭疽病病原体的宿主抗性基因。在这里，我们报道了在黄瓜自交系 Gy14 和 WI 2757 中对炭疽病 1 号病原体的抗性基因的精细图谱定位和克隆。在多个群体中的表型和 QTL 分析表明，单个隐性基因 cla 是这两个系中炭疽病抗性的基础，但 WI2757 携带一个额外的次要效应 QTL。使用 150 个 Gy14 × 9930 重组自交系和 1043 个 F 个体的精细图谱定位将 cla 基因座限定在黄瓜染色体 5 上的 32kb 区域内，其中包含三个预测基因。多种证据表明，黄瓜 STAYGREEN（CsSGR）基因是炭疽病抗性基因的候选基因。CsSGR 第三外显子中的单个核苷酸突变导致 Gy14 中 9930 的谷氨酰胺突变为精氨酸，这似乎是 Gy14 和 9930 之间炭疽病接种反应差异的原因。定量实时 PCR 分析表明，在易感 9930 中炭疽病病原体接种后，CsSGR 显著上调，而在抗性 Gy14 中其表达水平要低得多。对自然黄瓜群体的等位基因多样性的研究表明，几乎所有美国来源的改良品种或育种系中的抗性等位基因均来自 PI 197087。这项工作揭示了高度保守的 STAYGREEN（SGR）家族基因在植物宿主抗病性中的未知功能。
