Piercing/sucking insects such as green peach aphid (GPA) (Myzus persicae) cause direct damage by obtaining phloem nutrients and indirect damage by spreading plant viruses. To investigate the response of peach trees (Prunus persica) to aphids, the leaf transcriptome and metabolome of two genotypes with different sensitivities to GPA were studied. The gene expression of aphid-susceptible plants infested with aphids was similar to that of control plants, whereas the gene expression of aphid-resistant plants infested with aphids showed strong induced changes in gene expression compared with control plants. Furthermore, gene transcripts in defense-related pathways, including plant-pathogen interaction, MAPK signaling, and several metabolic pathways, were strongly enriched upon aphid infestation. Untargeted secondary metabolite profiling confirmed that aphid infestation induced larger changes in aphid-resistant than in aphid-susceptible peaches. Consistent with transcriptomic alterations, nine triterpenoids showed highly significant GPA-induced accumulation in aphid-resistant peaches, whereas triterpenoid abundance remained predominantly unchanged or undetected in aphid-susceptible peaches. Furthermore, some types of transcription factors (including WRKYs, ERFs, and NACs) were strongly induced upon GPA infestation in aphid-resistant, but not in aphid-susceptible peaches. These results suggested that the accumulation of specialized triterpenoids and the corresponding pathway transcripts may play a key role in peach GPA resistance.

植物生长过程中,时刻面对植食性昆虫的威胁,如营养生长以及生殖生长、叶子和嫩枝.昆虫对于寄主植物的直接伤害来自对寄主植物取食,分为吸取植物汁液和咀嚼植物组织2种方式.此外,昆虫取食会对植物造成多种疾病,从而导致间接植物受损.为应对昆虫的攻击,植物会产生一些生物活性化合物(包括三萜皂苷),以增强它们对食草昆虫的防御能力.萜类是植物代谢物中种类最多的一类,在植物生长和发育中,它们被广泛用于维持各种基本功能,很多数萜类化合物,如三萜皂苷,在植物应对非生物和生物胁迫过程中行使特定的保护作用.本文阐述了植物中三萜皂苷代谢产物在抵御昆虫危害过程中的最重要功能,并概述了对三萜皂苷类代谢途径、调节和多样化理解的最新进展.因此,植物生物活性化合物的研究有助于不同生态系统中的害虫综合治理.

【Objective】The objective of this study is to clarify the underlying biochemical mechanisms related to the resistance and susceptibility of peach towards Myzus persicae, and to identify the key secondary metabolites of peach responding to the M. persicae infection.【Method】New shoots of resistant (‘96-5-1’ (9651), ZaoYouTao (ZYT)) and susceptible (Zhong You 13 (CN13), Zhong Nong Jin Hui (ZNJH)) peach trees were inoculated with M. persicae for 3 days and used for secondary metabolite extraction and UPLC-MS/MS analysis. Differentially altered metabolites (DAMs) were screened with |log2 fold change|≥1, P-value≤0.01 as threshold. The VIP value of the OPLS-DA model was used to perform differences between resistant and susceptible peach.【Result】To illustrate the biochemical mechanisms of M. persicae resistance in peach, aphid-resistant/aphid-susceptible peach varieties infested with M. persicae for 3 days. A total of 528 metabolites were identified in the treated samples through widely targeted metabolomics analysis. Using principal component analysis (PCA), hierarchical cluster analysis (HCA) and Venn diagram analysis, it was found that 7 DAMs were identified from the susceptible variety CN13, and 2 of them were significantly decreased, 5 of them were significantly increased. 7 DAMs were identified from the susceptible variety ZNJH, and 3 of them were significantly decreased, 4 of them were significantly increased. 33 DAMs were identified from the resistant variety ‘96-5-1’, and 1 of them was significantly decreased, 32 of them were significantly increased. 55 DAMs were identified from the resistant variety ZYT, and 12 of them were significantly decreased, 43 of them were significantly increased. The majority of the DAMs were identified from the two resistant varieties, and the overall magnitude of change was greater in the resistant varieties than that in the susceptible varieties. Finally, 15 secondary metabolites (6 amino acids and their derivatives, 5 phenolic acids, 3 nucleotides and their derivatives, and 1 organic acid) were considered to be involved in M. persicae resistance of ‘Shou xing tao’.【Conclusion】The significantly up-regulated secondary metabolites obtained in M. persicae-resistant peach varieties were mainly involved in the response to M. persicae feeding. The regulation of these secondary metabolites (amino acids and their derivatives, phenolic acids, nucleotides and their derivatives, organic acid) is the important mechanism of defense reaction to M. persicae.

The green peach aphid (GPA), Myzus persicae, is a polyphagous, sap-sucking aphid and a vector of many plant viruses. In peach, Prunus persica, three individual dominant GPA resistance loci have been genetically defined (Rm1-3), but knowledge of the underlying genes is limited. In this study, we focused on the Rm3 locus. Bulk segregant analysis (BSA) mapping in segregating progeny populations delimited Rm3 to an interval spanning 160 kb containing 21 genes on chromosome 1. RNA-seq data provided no evidence of candidate genes, but chromosomal structural variations were predicted around a nucleotide-binding site-leucine-rich repeat (NLR) gene (ppa000596m) within the Rm3 fine-mapping interval. Following bacterial artificial chromosome (BAC) library construction for a GPA-resistant peach cultivar and the sequencing of three target BAC clones, a chromosomal structural variation encompassing two novel TIR-NLR-class disease resistance (R) protein-coding genes was identified, and the expressed NLR gene (NLR1) was identified as a candidate for M. persicae resistance. Consistent with its proposed role in controlling GPA resistance, NLR1 was only expressed in the leaves of resistant peach phenotypes. A molecular marker that was designed based on the NLR1 sequence co-segregated with the GPA-resistant phenotype in four segregating populations, 162 peach cultivars, and 14 wild relatives, demonstrating the dominant inheritance of the Rm3 locus. Our findings can be exploited to facilitate future breeding for GPA-resistance in peach.

桃蚜(Myzus persicae Sülzer)是春季危害桃树最严重的害虫,它通过取食叶片、分泌蜜露危害叶片,进而影响叶片进行光合作用,同时它还是植物病毒的携带者和传播媒介(图1).目前防治桃蚜仍然依赖于喷施农药,长此以往不仅桃蚜会产生抗性,还会给环境带来污染.利用树体自身的抗性进行桃蚜防控是最为环保和经济的防控方式.本研究中,笔者通过观察桃不同类型抗蚜材料上人工外接桃蚜后,桃树抗蚜材料的抗性表型和蚜虫的取食行为,能够加深对桃树抗蚜材料抗性表现的认识,为未来抗蚜机制的深入分析提供借鉴.

[目的]桃蚜(Myzus persicae)是春季对桃树危害最大的害虫,严重影响了桃产业的绿色健康发展.利用树体自身抗性进行桃树蚜虫防控是最为环保和经济的方式,而筛选桃树抗蚜种质资源是抗性利用的先决条件.[方法]以栽培种来源的抗蚜材料09南3-30为试材,通过抗性表型观察,结合系谱分析、遗传分析和集群分离分析(Bulk Segregant Analysis,BSA)定位的方法对该试材的新颖性进行了评价.[结果]在本研究中首次报道了一类新的栽培种抗蚜材料09南3-30.09南3-30具有强烈的趋避性桃蚜抗性,结合系谱分析表明该材料区别于以往毛桃和山桃类抗蚜材料.基于群体的遗传规律分析表明,这种抗性受到单基因或主效数量性状座位(Quantitative Trait Locus,QTL)基因控制.以桃树中桃红玉×09南3-30杂交F,群体为试验材料,基于二代测序的BSA集群分离分析法,将该抗性定位到了桃第3号染色体的特定区段.[结论]09南3-30的抗蚜表型、结合系谱分析、遗传分析和定位分析都表明其为一类来自于桃栽培种的新型抗蚜资源.