U.S. Vegetable Laboratory, USDA, ARS, 2700 Savannah Highway, Charleston, SC, 29414, USA.
Department of Biology, Claflin University, Orangeburg, SC, 29115, USA.
Sci Rep. 2020 Aug 20;10(1):14038. doi: 10.1038/s41598-020-70932-z.
Watermelon is an important vegetable crop and is widely cultivated in USA with an approximate global production of > 100 million tons. Powdery mildew (PM) caused by Podosphaera xanthii is a major production-limiting factor on watermelon and other cucurbits. Numerous PM and multiple disease resistant (MDR) watermelon germplasm lines have been developed by the USDA in Charleston, SC. To gain a better understanding of the innate and activated molecular defense mechanisms involved during compatible and incompatible PM-watermelon interactions, we inoculated PM susceptible (USVL677-PMS) and resistant (USVL531-MDR) watermelon plants with 10 conidia ml of P. xanthii. RNA-seq profiling was done on leaf samples collected at 0, 1, 3, and 8 days post inoculation (DPI). A total of 2,566 unique differentially expressed genes (DEGs) were identified between compatible and incompatible interactions with P. xanthii. The compatible interactions resulted in distinct plant gene activation (> twofold unique transcripts, 335:191:1762 :: 1:3:8 DPI) as compared to incompatible interaction (> twofold unique transcripts, 314:681:487 :: 1:3:8 DPI). Further, comparative whole-genome resequencing analysis of USVL531-PMR, USVL677-PMS and four introgressed PM resistant recombinant inbred lines (RIL, USVL531-PMR × USVL677-PMS) were performed to identify the region of PM resistance introgressed break points along with other traits inherent by USVL531-PMR by comparing the SNPs and InDels. Based on SNPs identification and CAPS markers, the resistance gene was identified as ClaPMR2, Citrullus lanatus PM Resistance gene 2 {Chr2 : 26750001 .. 26753327 (-)}, a NBS-LRR resistance protein (R) with homology to the Arabidopsis thaliana PM resistance protein, RPW8. The transcriptome data also revealed a complex regulatory network associated with the introgressed junctions mediated by PM resistance R proteins (R genes) that may involve multiple signal regulators and transducers, carbohydrate metabolism, cell wall modifications and the hormone-signaling pathway.
西瓜是一种重要的蔬菜作物，在美国广泛种植，全球产量超过 1 亿吨。由瓜白粉菌（Podosphaera xanthii）引起的白粉病是西瓜和其他葫芦科作物的主要生产限制因素。美国农业部在南卡罗来纳州查尔斯顿已经开发了许多白粉病和多种疾病抗性（MDR）西瓜种质系。为了更好地了解在亲和和不亲和白粉病-西瓜相互作用过程中涉及的固有和激活的分子防御机制，我们用 10 个分生孢子 ml 的瓜白粉菌接种易感（USVL677-PMS）和抗性（USVL531-MDR）西瓜植株。在接种后 0、1、3 和 8 天（dpi）采集叶片样本进行 RNA-seq 分析。在与瓜白粉菌的亲和和不亲和相互作用中，共鉴定出 2566 个差异表达基因（DEGs）。与不亲和相互作用相比（2 倍以上独特转录物，314:681:487：1:3:8dpi），亲和相互作用导致明显的植物基因激活（>2 倍独特转录物，335:191:1762：1:3:8dpi）。此外，对 USVL531-PMR、USVL677-PMS 和四个导入白粉病抗性重组自交系（RIL，USVL531-PMR×USVL677-PMS）进行全基因组重测序分析，以鉴定导入的 PM 抗性片段的断点区域以及 USVL531-PMR 固有的其他性状，通过比较 SNPs 和 InDels。基于 SNPs 鉴定和 CAPS 标记，将抗性基因鉴定为 ClaPMR2，甜瓜白粉病抗性基因 2{Chr2：26750001..26753327（-）}，一种 NBS-LRR 抗性蛋白（R），与拟南芥白粉病抗性蛋白 RPW8 同源。转录组数据还揭示了一个与导入的由 PM 抗性 R 蛋白（R 基因）介导的 junctions 相关的复杂调控网络，该网络可能涉及多个信号调节剂和传感器、碳水化合物代谢、细胞壁修饰和激素信号通路。
