Department of Plant Pathology, College of Plant Protection, Shandong Agricultural University, Tai'an, China.
Shandong Key Laboratory for Green Prevention and Control of Agricultural Pests, Institute of Plant Protection, Shandong Academy of Agricultural Sciences, Ji'nan, China.
Mol Plant Pathol. 2024 Nov;25(11):e70033. doi: 10.1111/mpp.70033.
Plant resistance, which acts as a selective pressure that affects viral population fitness, leads to the emergence of resistance-breaking virus strains. Most recessive resistance to potyviruses is related to the mutation of eukaryotic translation initiation factor 4E (eIF4E) or its isoforms that break their interactions with the viral genome-linked protein (VPg). In this study, we found that the VPg α1-α2 loop, which is essential for binding eIF4E, is the most variable domain of papaya ringspot virus (PRSV) VPg. PRSV VPg with the naturally occurring amino acid substitution of K105Q or E108G in the α1-α2 loop fails to interact with watermelon (Citrullus lanatus) eIF4E but interacts with watermelon eIF(iso)4E instead. Moreover, PRSV carrying these mutations can break the eIF4E-mediated resistance to PRSV in watermelon accession PI 244019. We further revealed that watermelon eIF(iso)4E with the amino acid substitutions of DNQS to GAAA in the cap-binding pocket could not interact with PRSV VPg with natural amino acid substitution of K105Q or E108G. Therefore, our finding provides a precise target for engineering watermelon germplasm resistant to resistance-breaking PRSV isolates.
植物抗性作为一种选择压力，影响病毒种群的适应性，导致抗性突破病毒株的出现。大多数对马铃薯 Y 病毒属病毒的隐性抗性与真核翻译起始因子 4E（eIF4E）或其同工型的突变有关，这些突变会破坏它们与病毒基因组连接蛋白（VPg）的相互作用。在本研究中，我们发现 VPg 的α1-α2 环是与 eIF4E 结合所必需的，是木瓜环斑病毒（PRSV）VPg 中最可变的结构域。PRSV VPg 的α1-α2 环中发生的自然氨基酸取代 K105Q 或 E108G 会导致其无法与西瓜（Citrullus lanatus）eIF4E 相互作用，而是与西瓜 eIF（iso）4E 相互作用。此外，携带这些突变的 PRSV 能够突破西瓜品种 PI 244019 中 eIF4E 介导的对 PRSV 的抗性。我们进一步揭示，西瓜 eIF（iso）4E 中的氨基酸取代 DNQS 为 GAAA 会使其无法与具有天然氨基酸取代 K105Q 或 E108G 的 PRSV VPg 相互作用。因此，我们的发现为工程化西瓜种质对抗性突破的 PRSV 分离株的抗性提供了一个精确的靶标。
