Kumar Rahul, Chanda Bidisha, Adkins Scott, Kousik Chandrasekar S
Agricultural Research Service (USDA-ARS), U.S. Vegetable Laboratory (USVL), United States Department of Agriculture, Charleston, SC, United States.
ORISE participant, USVL, USDA-ARS, Charleston, SC, United States.
Front Plant Sci. 2024 Aug 2;15:1426647. doi: 10.3389/fpls.2024.1426647. eCollection 2024.
Watermelon () is the third largest fruit crop in the world in term of production. However, it is susceptible to several viruses. Watermelon vine decline (WVD), caused by whitefly-transmitted squash vein yellowing virus (SqVYV), is a disease that has caused over $60 million in losses in the US and continues to occur regularly in southeastern states. Understanding the molecular mechanisms underlying resistance to SqVYV is important for effective disease management. A time-course transcriptomic analysis was conducted on resistant (392291-VDR) and susceptible (Crimson Sweet) watermelon genotypes inoculated with SqVYV. Significantly higher levels of SqVYV were observed over time in the susceptible compared to the resistant genotype. The plasmodesmata callose binding protein () gene, which is responsible for increased callose deposition in the plasmodesmata, was more highly expressed in the resistant genotype than in the susceptible genotype before and after inoculation, suggesting the inhibition of cell-to-cell movement of SqVYV. The potential role of the RNA interference (RNAi) pathway was observed in the resistant genotype based on differential expression of eukaryotic initiation factor (), translin, DICER, ribosome inactivating proteins, RNA-dependent RNA polymerase (), and Argonaute () genes after inoculation. The significant differential expression of hormone-related genes, including those involved in the ethylene, jasmonic acid, auxin, cytokinin, gibberellin, and salicylic acid signaling pathways, was observed, emphasizing their regulatory roles in the defense response. Genes regulating pectin metabolism, cellulose synthesis, cell growth and development, xenobiotic metabolism, and lignin biosynthesis were overexpressed in the susceptible genotype, suggesting that alterations in cell wall integrity and growth processes result in disease symptom development. These findings will be helpful for further functional studies and the development of SqVYV-resistant watermelon cultivars.
就产量而言，西瓜是世界上第三大水果作物。然而，它易受多种病毒感染。由粉虱传播的南瓜叶脉黄化病毒（SqVYV）引起的西瓜藤蔓衰退（WVD）是一种在美国造成了超过6000万美元损失且在东南部各州仍经常发生的病害。了解抗SqVYV的分子机制对于有效的病害管理至关重要。对接种了SqVYV的抗性（392291-VDR）和易感（绯红甜心）西瓜基因型进行了时间进程转录组分析。随着时间的推移，与抗性基因型相比，易感基因型中观察到的SqVYV水平显著更高。负责在胞间连丝中增加胼胝质沉积的胞间连丝胼胝质结合蛋白（）基因，在接种前后在抗性基因型中的表达均高于易感基因型，这表明SqVYV的细胞间移动受到了抑制。基于接种后真核起始因子（）、转位蛋白、Dicer、核糖体失活蛋白、RNA依赖的RNA聚合酶（）和AGO蛋白（）基因的差异表达，在抗性基因型中观察到了RNA干扰（RNAi）途径的潜在作用。观察到了激素相关基因的显著差异表达，包括那些参与乙烯、茉莉酸、生长素、细胞分裂素、赤霉素和水杨酸信号通路的基因，这强调了它们在防御反应中的调节作用。调节果胶代谢、纤维素合成、细胞生长和发育、异源物质代谢以及木质素生物合成的基因在易感基因型中过表达，这表明细胞壁完整性和生长过程的改变导致了病害症状的发展。这些发现将有助于进一步的功能研究以及培育抗SqVYV的西瓜品种。
