https://mp.weixin.qq.com/s/559wuIZDO3eejqzT7vFPmQ

近日，山東農(nóng)大李向東-耿超團(tuán)隊(duì)在MPP發(fā)表了題為《The Naturally Occurring Amino Acid Substitution in the VPg α1–α2 Loop Breaks eIF4E-Mediated Resistance to PRSV by Enabling VPg to Re-Hijack Another eIF4E Isoform eIF(iso)4E in Watermelon》的研究論文，揭示了VPgα1-α2環(huán)中的天然氨基酸取代通過使VPg重新劫持eIF4E異構(gòu)體來破壞PRSV抗性。

植物抗性是一種影響病毒種群適應(yīng)性的選擇壓力，導(dǎo)致t突破抗性病毒株的出現(xiàn)。大多數(shù)對馬鈴薯Y病毒的隱性抗性與真核翻譯起始因子4E（eIF4E）或其異構(gòu)體的突變有關(guān)，這些突變破壞了它們與病毒基因組連接蛋白（VPg）的相互作用。

在這項(xiàng)研究中，作者發(fā)現(xiàn)VPgα1-α2環(huán)是番木瓜環(huán)斑病毒（PRSV）VPg最可變的結(jié)構(gòu)域，是結(jié)合eIF4E所必需的。α1-α2環(huán)中天然存在的K105Q或E108G氨基酸取代的PRSV VPg不能與西瓜eIF4E相互作用，而是與西瓜eIF（iso）4E相互作用。

此外，攜帶這些突變的PRSV可以在西瓜（登錄號(hào)PI 244019）中打破eIF4E介導(dǎo)的對PRSV的抗性。作者進(jìn)一步揭示，在帽結(jié)合袋中具有DNQS到GAAA氨基酸置換的西瓜eIF（iso）4E不能與具有K105Q或E108G天然氨基酸置換的PRSV VPg相互作用。

因此，本研究的發(fā)現(xiàn)為工程化西瓜種質(zhì)資源抗突破抗性的PRSV分離物提供了一個(gè)精確的靶標(biāo)。

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.

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