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

Abstract

The oomycete Phytophthora infestans, the cause of late blight, is one of the most important potato pathogens. During infection, it secretes effector proteins that manipulate host cell function, thus contributing to pathogenicity. This study examines sequence differentiation of two P. infestans effectors from 91 isolates collected in Poland and Norway and five reference isolates. A gene encoding the Avr-vnt1 effector, recognized by the potato Rpi-phu1 resistance gene product, is conserved. In contrast, the second effector, AvrSmira1 recognized by Rpi-Smira1, is highly diverse. Both effectors contain positively selected amino acids. A majority of the polymorphisms and all selected sites are located in the effector C-terminal region, which is responsible for their function inside host cells. Hence it is concluded that they are associated with a response to diversified target protein or recognition avoidance. Diversification of the AvrSmira1 effector sequences, which existed prior to the large-scale cultivation of plants containing the Rpi-Smira1 gene, may reduce the predicted durability of resistance provided by this gene. Although no isolates virulent to plants with the Rpi-phu1 gene were found, the corresponding Avr-vnt1 effector has undergone selection, providing evidence for an ongoing 'arms race' between the host and pathogen. Both genes remain valuable components for resistance gene pyramiding.

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

“…sequences. This level of genetic diversity is comparable with other effector genes, including Avr3a, Avr2, and AvrSmira1 but higher than other functional genes such as eEF-1α, cox1, and β-tubulin genes of P. infestans (Cárdenas et al, 2011;Stefańczyk et al, 2018;Yang et al, 2018;Wang et al, 2020). This result is consistent with evolutionary theory postulating that genomes involved in antagonistic interactions such as effector genes tend to evolve at an increased speed (Stukenbrock and McDonald, 2009;Karasov et al, 2014;Möller and Stukenbrock, 2017).…”

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

“…The high rate of evolution in effector genes such as Avr1 facilitates the generation of new invasive mechanisms, which allow the pathogen to escape host defenses [16]. This creates an advantage for the survival and reproduction of the pathogen and contributes to the quick breakdown of host resistance in the potato and many other crops [60][61][62][63]. R1 is the first gene introgressed from S. demissum to cultivated potato crops for late blight resistance.…”

Identification of Natural Resistance Mediated by Recognition of Phytophthora infestans Effector Gene Avr3aEM in Potato

“…Because of its polymorphism, it is associated with a response to a diversified target protein or recognition avoidance (Pel et al, 2009;Pais et al, 2017). Longshu7 showed HR toward Avrvnt1.1, suggesting that it carries the functional Rpi-vnt1 gene which may provide a high level and wide-spectrum late blight resistance (Stefańczyk et al, 2018).…”