Analysis of polymorphism and transcription of the effector gene Avr1b in Phytophthora sojae isolates from China virulent to Rps1b

Abstract

The effector gene Avr1b-1 of Phytophthora sojae determines the efficacy of the resistance gene Rps1b in soybean. The sequences of the Avr1b-1 locus in 34 Chinese isolates of P. sojae were obtained and analysed by polymerase chain reaction (PCR) and inverse PCR. Four different alleles and a complete deletion mutation of the Avr1b-1 gene were identified. Molecular analysis of the deletion breakpoints in the Avr1b-1 locus revealed that an 8-kb DNA sequence containing Avr1b-1 was deleted and a 12.7-kb DNA sequence was inserted at the same locus. A truncated transposase gene was found and five transposable elements were predicted in the inserted sequence, suggesting that the deletion of Avr1b-1 might be attributed to transposon movement. The transcription of Avr1b-1 was analysed in virulent isolates containing four alleles of Avr1b-1 by real-time reverse transcription-PCR. In all virulent isolates, only those isolates containing the second allele transcripted Avr1b-1.

From pathogen genomes to host plant processes: the power of plant parasitic oomycetes

“…Transcriptional silencing of effector genes is one of the mechanisms that plant pathogenic oomycetes deploy to avoid the activation of host R -gene-mediated immunity. A few examples have been described for races of P. infestans and P. sojae in which the expression of specific RXLR effectors is correlated with their virulence or avirulence on specific host genotypes [29,55-59]. In P. sojae , these transcriptional polymorphisms have been attributed to insertions or deletions in the promoter region [55,57,59].…”

Polymorphism in natural alleles of the avirulence gene Avr1c is associated with the host adaptation of Phytophthora sojae

“…Many Avr effectors escape recognition by cognate Rps genes in P. sojae by deletion, such as Avr1a, Avr1b, Avr1c and Avr1d (Qutob et al 2009;Cui et al 2012;Na et al 2013;Na et al 2014;Arsenault-Labrecque et al 2018). In three isolates, Avr1c was deleted in an 8.8 kb or 10.8 kb region containing two copies of Avr1a, one copy of Avr1c, and one copy of Avh72 (Na et al 2014;Arsenault-Labrecque et al 2018).…”

“…Point mutations and loss of transcript of Avr1b-1 induced virulence (Shan et al 2004). In addition, the transposable elements insertion resulted in deletion of Avr1b-1 from Chinese isolates (Cui et al 2012). Avr1d is present in P. sojae strains avirulent to Rps1d, but is absent from the genome of virulent strains (Na et al 2013).…”

SCR96, a small cysteine‐rich secretory protein of Phytophthora cactorum, can trigger cell death in the Solanaceae and is important for pathogenicity and oxidative stress tolerance

“…Studies have shown how the primary sequences of host‐translocated effectors have been shaped by positive selection, and how genes undergo accelerated birth and death evolution (Cui et al ., ; Stassen and Van den Ackerveken, ; Win et al ., ). In this study, sequence polymorphism was not observed for SCR96.…”