Higher Copy Numbers of the Potato RB Transgene Correspond to Enhanced Transcript and Late Blight Resistance Levels

Late blight of potato ranks among the costliest of crop diseases worldwide. Host resistance offers the best means for controlling late blight, but previously deployed single resistance genes have been short-lived in their effectiveness. The foliar blight resistance gene RB, previously cloned from the wild potato Solanum bulbocastanum, has proven effective in greenhouse tests of transgenic cultivated potato. In this study, we examined the effects of the RB transgene on foliar late blight resistance in transgenic cultivated potato under field production conditions. In a two-year replicated trial, the RB transgene, under the control of its endogenous promoter, provided effective disease resistance in various genetic backgrounds, including commercially prominent potato cultivars, without fungicides. RB copy numbers and transcript levels were estimated with transgene-specific assays. Disease resistance was enhanced as copy numbers and transcript levels increased. The RB gene, like many other disease resistance genes, is constitutively transcribed at low levels. Transgenic potato lines with an estimated 15 copies of the RB transgene maintain high RB transcript levels and were ranked among the most resistant of 57 lines tested. We conclude that even in these ultra–high copy number lines, innate RNA silencing mechanisms have not been fully activated. Our findings suggest resistance-gene transcript levels may have to surpass a threshold before triggering RNA silencing. Strategies for the deployment of RB are discussed in light of the current research.

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New Findings on the Resistance Mechanism of an Elite Diploid Wild Potato Species JAM1-4 in Response to a Super Race Strain of Phytophthora infestans

Phytopathology ◽

10.1094/phyto-09-19-0331-r ◽

2020 ◽

Vol 110 (8) ◽

pp. 1375-1387

Author(s):

Jiayi Zheng ◽

Shaoguang Duan ◽

Miles R. Armstrong ◽

Yanfeng Duan ◽

Jianfei Xu ◽

...

Keyword(s):

Disease Resistance ◽

Late Blight ◽

Phytophthora Infestans ◽

Resistance Genes ◽

Resistance Mechanism ◽

Late Blight Resistance ◽

Blight Resistance ◽

Resistance Response ◽

Potato Disease ◽

New Findings

Late blight is a devastating potato disease worldwide, caused by Phytophthora infestans. The P. infestans strain 2013-18-306 from Yunnan is a “supervirulent race” that overcomes all 11 known late blight resistance genes (R1 to R11) from Solanum demissum. In a previous study, we identified a diploid wild-type potato JAM1-4 (S. jamesii) with high resistance to 2013-18-306. dRenSeq analysis indicated the presence of novel R genes in JAM1-4. RNA-Seq was used to analyze the late blight resistance response genes and defense regulatory mechanisms of JAM1-4 against 2013-18-306. Gene ontology enrichment and KEGG pathway analysis showed that many disease-resistant pathways were significantly enriched. Analysis of differentially expressed genes (DEGs) revealed an active disease resistance mechanism of JAM1-4, and the essential role of multiple signal transduction pathways and secondary metabolic pathways comprised of SA-JA-ET in plant immunity. We also found that photosynthesis in JAM1-4 was inhibited to promote the immune response. Our study reveals the pattern of resistance-related gene expression in response to a super race strain of potato late blight and provides a theoretical basis for further exploration of potato disease resistance mechanisms, discovery of new late blight resistance genes, and disease resistance breeding.

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Two Tomato (Solanum lycopersicum) Thaumatin-like Protein Genes Confer Enhanced Resistance to Late Blight (Phytophthora infestans)

Phytopathology ◽

10.1094/phyto-06-20-0237-r ◽

2021 ◽

Author(s):

Haishan Zhu ◽

Minghua Deng ◽

Zhengan Yang ◽

Lianzhen Mao ◽

Shurui Jiang ◽

...

Keyword(s):

Disease Resistance ◽

Late Blight ◽

Phytophthora Infestans ◽

Resistance Genes ◽

Single Gene ◽

Expression Patterns ◽

Late Blight Resistance ◽

Inbred Lines ◽

Blight Resistance ◽

Tomato Production

Late blight (caused by Phytophthora infestans) poses a serious threat to tomato production, but the number of late blight resistance genes isolated from tomato is limited, making resistance gene mining a high research priority. In this study, highly resistant CLN2037E and susceptible No.5 tomato inbred lines were used to identify late blight resistance genes. Using transcriptome sequencing, we discovered 36 differentially expressed genes (DEGs), including 21 nucleotide binding site-leucine-rich repeat (NBS-LRR) and 15 pathogenesis-related (PR) disease resistance genes. Cluster analysis and real-time quantitative PCR (RT-qPCR) showed that these 36 genes possessed similar expression patterns in different inbred lines after inoculation with P. infestans. Moreover, two PR genes with unique responses were chosen to verify their functions when exposed to P. infestans: Solyc08g080660 and Solyc08g080670, both of which were thaumatin-like protein (TLP) genes and were clustered in the tomato genome. Functions of these two genes were identified by gene overexpression and gene editing technology. Overexpression and knockout of single Solyc08g080660 and Solyc08g080670 corresponded to an increase and decrease in resistance to late blight, respectively, and Solyc08g080660 led to a greater change in disease resistance compared with Solyc08g080670. Co-transformation of dual genes resulted in a much greater effect than any single gene. This study provides novel candidate resistance genes for tomato breeding against late blight and insights into the interaction mechanisms between tomato and P. infestans.

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Two orthologs of late blight resistance gene R1 in wild and cultivated potato

Russian Journal of Plant Physiology ◽

10.1134/s1021443717050028 ◽

2017 ◽

Vol 64 (5) ◽

pp. 718-727 ◽

Cited By ~ 2

Author(s):

M. P. Beketova ◽

E. A. Sokolova ◽

E. V. Rogozina ◽

M. A. Kuznetsova ◽

E. E. Khavkin

Keyword(s):

Late Blight ◽

Resistance Gene ◽

Late Blight Resistance ◽

Blight Resistance ◽

Cultivated Potato

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Transcriptome analysis of scions grafted to potato rootstock for improving late blight resistance

10.21203/rs.3.rs-58639/v2 ◽

2020 ◽

Author(s):

Yuexin Li ◽

Degang Zhao

Keyword(s):

Disease Resistance ◽

Late Blight ◽

Protein Kinases ◽

Molecular Mechanisms ◽

Late Blight Resistance ◽

Potato Late Blight ◽

Susceptible Variety ◽

Resistant Variety ◽

Blight Resistance ◽

Expression Levels

Abstract Background: Late blight seriously threatens potato cultivation worldwide. The severe and widespread damage caused by the fungal pathogen can lead to drastic decreases in potato yield. Although grafting technology has been widely used to improve crop resistance, the effects of grafting on potato late blight resistance as well as the associated molecular mechanisms remain unclear. Therefore, we performed RNA transcriptome sequencing analysis and the late blight resistance testing of the scion when the potato late blight-resistant variety Qingshu 9 and the susceptible variety Favorita were used as the rootstock and scion, respectively, and vice versa. The objective of this study was to evaluate the influence of the rootstock on scion disease resistance and to clarify the related molecular mechanisms.Results: A Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that the expression levels of genes related to plant–pathogen interactions, plant mitogen-activated protein kinase (MAPK) signaling pathways, and plant hormone signal transduction pathways were significantly up-regulated in the scion when Qingshu 9 was used as the rootstock. These genes included late blight response genes encoding calcium-dependent protein kinases (CDPKs), chitin elicitor receptor kinases (CERKs), LRR receptor serine/threonine protein kinases (LRR-LRKs), NPR family proteins in the salicylic acid synthesis pathway, and MAPKs. When Favorita was used as the rootstock, the expression levels of the late blight response genes were not up-regulated in the Qingshu 9 scion, but the expression levels of the genes related to proline metabolism, fatty acid chain elongation, and diterpenoid biosynthesis pathways were down-regulated. Resistance results showed that self-grafting of the susceptible variety and grafting with the resistant variety as the rootstock increased the resistance of the susceptible scion to late blight. However, the resistance was stronger after grafting with the resistant variety as the rootstock. Using the susceptible variety as the rootstock decreased the late blight resistance of the resistant scion.Conclusions: Our results showed that changes to the expression of disease resistance genes in the scion after grafting are associated with late blight resistance. The results provide the basis for exploring the molecular mechanism underlying the effects of rootstocks on scion disease resistance.

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Detection of Novel QTLs for Late Blight Resistance Derived from the Wild Potato Species Solanum microdontum and Solanum pampasense

Genes ◽

10.3390/genes11070732 ◽

2020 ◽

Vol 11 (7) ◽

pp. 732

Author(s):

Fergus Meade ◽

Ronald Hutten ◽

Silke Wagener ◽

Vanessa Prigge ◽

Emmet Dalton ◽

...

Keyword(s):

Late Blight ◽

Resistance Genes ◽

Late Blight Resistance ◽

Gene Clusters ◽

Genetic Maps ◽

Blight Resistance ◽

Wild Potato ◽

Wild Potato Species ◽

Potato Species ◽

Solanum Microdontum

Wild potato species continue to be a rich source of genes for resistance to late blight in potato breeding. Whilst many dominant resistance genes from such sources have been characterised and used in breeding, quantitative resistance also offers potential for breeding when the loci underlying the resistance can be identified and tagged using molecular markers. In this study, F1 populations were created from crosses between blight susceptible parents and lines exhibiting strong partial resistance to late blight derived from the South American wild species Solanum microdontum and Solanum pampasense. Both populations exhibited continuous variation for resistance to late blight over multiple field-testing seasons. High density genetic maps were created using single nucleotide polymorphism (SNP) markers, enabling mapping of quantitative trait loci (QTLs) for late blight resistance that were consistently expressed over multiple years in both populations. In the population created with the S. microdontum source, QTLs for resistance consistently expressed over three years and explaining a large portion (21–47%) of the phenotypic variation were found on chromosomes 5 and 6, and a further resistance QTL on chromosome 10, apparently related to foliar development, was discovered in 2016 only. In the population created with the S. pampasense source, QTLs for resistance were found in over two years on chromosomes 11 and 12. For all loci detected consistently across years, the QTLs span known R gene clusters and so they likely represent novel late blight resistance genes. Simple genetic models following the effect of the presence or absence of SNPs associated with consistently effective loci in both populations demonstrated that marker assisted selection (MAS) strategies to introgress and pyramid these loci have potential in resistance breeding strategies.

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Performance of Transgenic Potato Containing the Late Blight Resistance Gene RB

Plant Disease ◽

10.1094/pdis-92-3-0339 ◽

2008 ◽

Vol 92 (3) ◽

pp. 339-343 ◽

Cited By ~ 52

Author(s):

Dennis A. Halterman ◽

Lara Colton Kramer ◽

Susan Wielgus ◽

Jiming Jiang

Keyword(s):

Late Blight ◽

Resistance Gene ◽

Late Blight Resistance ◽

Transgenic Potato ◽

Field Trials ◽

Blight Resistance ◽

Solanum Bulbocastanum ◽

Wild Potato Species ◽

Foliar Resistance ◽

In The Wild

Late blight of potato, caused by Phytophthora infestans, is one of the most devastating diseases of potato. A major late blight resistance gene, called RB, previously was identified in the wild potato species Solanum bulbocastanum through map-based cloning. The full-length gene coding sequence, including the open reading frame and promoter, has been integrated into cultivated potato (S. tuberosum) using Agrobacterium-mediated transformation. RB-containing transgenic plants were challenged with P. infestans under optimal late blight conditions in greenhouse experiments. All transgenic lines containing RB exhibited strong foliar resistance. Field-grown transgenic tubers also were tested for resistance to P. infestans. In contrast to the foliar resistance phenotype, RB-containing tubers did not exhibit increased resistance. Two years of field trials were used to ascertain whether the presence of RB had any effect on tuber yield. We were unable to detect any significant effect on tuber size or yield after addition of the resistance gene to several S. tuberosum cultivars.

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Changes in Disease Resistance Phenotypes Associated With Plant Physiological Age Are Not Caused by Variation in R Gene Transcript Abundance

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-22-3-0362 ◽

2009 ◽

Vol 22 (3) ◽

pp. 362-368 ◽

Cited By ~ 21

Author(s):

Benjamin P. Millett ◽

Dimitre S. Mollov ◽

Massimo Iorizzo ◽

Domenico Carputo ◽

James M. Bradeen

Keyword(s):

Disease Resistance ◽

Late Blight ◽

Transcript Abundance ◽

Plant Age ◽

Physiological Age ◽

Blight Resistance ◽

Gene Transcript ◽

R Gene ◽

Transcript Levels ◽

Foliar Blight

Foliar late blight is one of the most important diseases of potato. Foliar blight resistance has been shown to change as a plant ages. In other pathosystems, resistance (R) gene transcript levels appear to be correlated to disease resistance. The cloning of the broad-spectrum, foliar blight resistance gene RB provided the opportunity to explore how foliar blight resistance and R-gene transcript levels vary with plant age. Plants of Solanum bulbocastanum PT29, from which RB, including the native promoter and other flanking regions, was cloned, and S. tuberosum cv. Dark Red Norland (nontransformed and RB-transformed) representing three different developmental stages were screened for resistance to late blight and RB transcript levels. Preflowering plants of all genotypes exhibited the highest levels of resistance, followed by postflowering and near-senescing plants. The RB transgene significantly affected resistance, enhancing resistance levels of all RB-containing lines, especially in younger plants. RB transgene transcripts were detected at all plant ages, despite weak correlation with disease resistance. Consistent transcript levels in plants of different physiological ages with variable levels of disease resistance demonstrate that changes in disease-resistance phenotypes associated with plant age cannot be attributed to changes in R-gene transcript abundance.

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