Accelerated cloning of a potato late blight–resistance gene using RenSeq and SMRT sequencing

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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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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Evaluation of the RPi-ber late blight resistance gene for tuber resistance in the field and laboratory

Plant Breeding ◽

10.1111/j.1439-0523.2010.01836.x ◽

2011 ◽

Vol 130 (4) ◽

pp. 464-468 ◽

Cited By ~ 4

Author(s):

Hilary Mayton ◽

Gilda Rauscher ◽

Ivan Simko ◽

William E. Fry

Keyword(s):

Late Blight ◽

Resistance Gene ◽

Late Blight Resistance ◽

Blight Resistance ◽

Tuber Resistance

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Characterisation of the late blight resistance in potato differential MaR9 reveals a qualitative resistance gene, R9a, residing in a cluster of Tm-2 2 homologs on chromosome IX

Theoretical and Applied Genetics ◽

10.1007/s00122-015-2480-6 ◽

2015 ◽

Vol 128 (5) ◽

pp. 931-941 ◽

Cited By ~ 18

Author(s):

Kwang-Ryong Jo ◽

Richard G. F. Visser ◽

Evert Jacobsen ◽

Jack H. Vossen

Keyword(s):

Late Blight ◽

Resistance Gene ◽

Late Blight Resistance ◽

Blight Resistance ◽

Qualitative Resistance

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

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-22-4-0437 ◽

2009 ◽

Vol 22 (4) ◽

pp. 437-446 ◽

Cited By ~ 72

Author(s):

James M. Bradeen ◽

Massimo Iorizzo ◽

Dimitre S. Mollov ◽

John Raasch ◽

Lara Colton Kramer ◽

...

Keyword(s):

Disease Resistance ◽

Late Blight ◽

Resistance Gene ◽

Resistance Genes ◽

Rna Silencing ◽

Late Blight Resistance ◽

Blight Resistance ◽

Transcript Levels ◽

Cultivated Potato ◽

Copy Numbers

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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