Diversity of Avr-vnt1
 and AvrSmira1
 effector genes in Polish and Norwegian populations of Phytophthora infestans

SummaryPathogen recognition by plants via pathogen-associated molecular patterns leads to PAMP-triggered immunity. However, pathogens can modulate it via the secretion of effectors. We hypothesize that in potato, induced defense triggered by a Phytophthora infestans concentrated culture filtrate (CCF) could alter both effector expression and disease severity.CCF was sprayed onto three potato genotypes with different resistance levels, before inoculation with P. infestans. Symptoms were scored visually at 1-4 dpi, while the expression of defense and effector genes was assessed by qRT-PCR.CCF induced most defense genes in Désirée (PRs, EIN3) and Bintje (PRs, PAL and POX), but repressed most defense genes in Rosafolia. On the contrary, CCF induced most effector genes in Rosafolia (Pi03192, Avrblb2, Avr3a, EPIC2B and SNE1). INF1 was over-expressed in Bintje, despite its earlier expression in both Désirée and Rosafolia compared to unsprayed controls. Pi03192 was repressed in Désirée, and was expressed earlier in Rosafolia than in controls. However, induced defense responses by CCF significantly reduced lesion areas at 3 dpi only in Désirée.The effectiveness of induced defense thus depends on host genotypes. It results from differential interactions and kinetics of defense and effector genes expressions.

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Identification of resistance locus and characterization of effector genes toward breeding for resistance to Phytophthora infestans

Acta Horticulturae ◽

10.17660/actahortic.2021.1316.2 ◽

2021 ◽

pp. 9-14

Author(s):

R.A. Arafa ◽

M.T. Rakha ◽

S.M. Kamel ◽

N.E.K. Soliman ◽

O.M. Moussa ◽

...

Keyword(s):

Phytophthora Infestans ◽

Resistance Locus ◽

Breeding For Resistance ◽

Effector Genes

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Effector Avr4 in Phytophthora infestans Escapes Host Immunity Mainly Through Early Termination

Frontiers in Microbiology ◽

10.3389/fmicb.2021.646062 ◽

2021 ◽

Vol 12 ◽

Author(s):

Abdul Waheed ◽

Yan-Ping Wang ◽

Oswald Nkurikiyimfura ◽

Wen-Yang Li ◽

Shi-Ting Liu ◽

...

Keyword(s):

Phytophthora Infestans ◽

Air Temperature ◽

Climatic Factors ◽

Isolation By Distance ◽

Plant Diseases ◽

Nucleotide Position ◽

Effector Gene ◽

Effector Genes ◽

Base Pair Deletion ◽

Mutation Mechanisms

Effector genes play critical roles in the antagonistic interactions between plants and pathogens. However, knowledge of mutation mechanisms and evolutionary processes in effector genes and the contribution of climatic factors to the evolution of effector genes are fragmented but important in sustainable management of plant diseases and securing food supply under changing climates. Here, we used a population genetic approach to explore the evolution of the Avr4 gene in Phytophthora infestans, the causal agent of potato blight. We found that the Avr4 gene exhibited a high genetic diversity generated by point mutation and sequence deletion. Frameshifts caused by a single base-pair deletion at the 194th nucleotide position generate two stop codons, truncating almost the entire C-terminal, which is important for effector function and R4 recognition in all sequences. The effector is under natural selection for adaptation supported by comparative analyses of population differentiation (FST) and isolation-by-distance between Avr4 sequences and simple sequence repeat marker loci. Furthermore, we found that local air temperature was positively associated with pairwise FST in the Avr4 sequences. These results suggest that the evolution of the effector gene is influenced by local air temperature, and the C-terminal truncation is one of the main mutation mechanisms in the P. infestans effector gene to circumvent the immune response of potato plants. The implication of these results to agricultural and natural sustainability in future climate conditions is discussed.

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Multiple Mechanisms Drive the Evolutionary Adaptation of Phytophthora infestans Effector Avr1 to Host Resistance

Journal of Fungi ◽

10.3390/jof7100789 ◽

2021 ◽

Vol 7 (10) ◽

pp. 789

Author(s):

Lin-Lin Shen ◽

Abdul Waheed ◽

Yan-Ping Wang ◽

Oswald Nkurikiyimfura ◽

Zong-Hua Wang ◽

...

Keyword(s):

Disease Management ◽

Phytophthora Infestans ◽

Host Resistance ◽

Population Genetic ◽

Base Substitution ◽

Intragenic Recombination ◽

Diversifying Selection ◽

Effector Gene ◽

Small Proteins ◽

Effector Genes

Effectors, a group of small proteins secreted by pathogens, play a central role in antagonistic interactions between plant hosts and pathogens. The evolution of effector genes threatens plant disease management and sustainable food production, but population genetic analyses to understand evolutionary mechanisms of effector genes are limited compared to molecular and functional studies. Here we investigated the evolution of the Avr1 effector gene from 111 Phytophthora infestans isolates collected from six areas covering three potato cropping regions in China using a population genetic approach. High genetic variation of the effector gene resulted from diverse mechanisms including base substitution, pre-termination, intragenic recombination and diversifying selection. Nearly 80% of the 111 sequences had a point mutation in the 512th nucleotide (T512G), which generated a pre-termination stop codon truncating 38 amino acids in the C-terminal, suggesting that the C-terminal may not be essential to ecological and biological functions of P. infestans. A significant correlation between the frequency of Avr1 sequences with the pre-termination and annual mean temperature in the collection sites suggests that thermal heterogeneity might be one of contributors to the diversifying selection, although biological and biochemical mechanisms of the likely thermal adaptation are not known currently. Our results highlight the risk of rapid adaptation of P. infestans and possibly other pathogens as well to host resistance, and the application of eco-evolutionary principles is necessary for sustainable disease management in agricultural ecosystems.

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