Editing of an effector gene promoter sequence impacts plant‐Phytophthora interaction

Abstract

Pathogen avirulence (Avr) effectors interplay with corresponding plant resistance (R) proteins and activate robust plant immune responses. Although the expression pattern of Avr genes has been tied to their functions for a long time, it is still not clear how Avr gene expression patterns impact plant‐microbe interactions. Here, we selected PsAvr3b, which shows a typical effector gene expression pattern from a soybean root pathogen Phytophthora sojae. To modulate gene expression, we engineered PsAvr3b promoter sequences by in situ substitution with promoter sequences from Actin (constitutive expression), PsXEG1 (early expression), and PsNLP1 (later expression) using the CRISPR/Cas9. PsAvr3b driven by different promoters resulted in distinct expression levels across all the tested infection time points. Importantly, those mutants with low PsAvr3b expression successfully colonized soybean plants carrying the cognate R gene Rps3b. To dissect the difference in plant responses to the PsAvr3b expression level, we conducted RNA‐sequencing of different infection samples at 24 h postinfection and found soybean immune genes, including a few previously unknown genes that are associated with resistance. Our study highlights that fine‐tuning in Avr gene expression impacts the compatibility of plant disease and provides clues to improve crop resistance in disease control management.

Phytophthora palmivora–Cocoa Interaction

“…However, recent work by Ochola and colleagues [ 128 ] may provide some clues as to how Avr gene expression impacts the compatibility of plant disease. By using the CRISPR/Cas9 engineering technique, PsAvr3b promoter sequences from P. sojae were substituted in situ with promoter sequences from Actin (constitutive expression), PsXEG1 (early expression), and PsNLP1 (later expression).…”

“…By using the CRISPR/Cas9 engineering technique, PsAvr3b promoter sequences from P. sojae were substituted in situ with promoter sequences from Actin (constitutive expression), PsXEG1 (early expression), and PsNLP1 (later expression). Compared to the wild type and the unedited mutant (T1) i.e., with the native PsAvr3b promoter as controls, PsAvr3b expression was significantly reduced when the PsAvr3b promoter was substituted with PsXEG1 (early expression) or PsNLP1 (late expression) promoters [ 128 ]. When these promoter mutants carrying PsXEG1 (X02 and X03) or PsNLP1 (N02 and N10) were tested on Williams (susceptible) and two resistant ( Rps3b and Rps3c ) soybean cultivars, these mutants gained virulence against the resistant Rps3b cultivar while mutants containing the PsACT promoter (A24 and A26) were unable to infect soybean cultivars carrying Rps3b [ 128 ].…”

“…Compared to the wild type and the unedited mutant (T1) i.e., with the native PsAvr3b promoter as controls, PsAvr3b expression was significantly reduced when the PsAvr3b promoter was substituted with PsXEG1 (early expression) or PsNLP1 (late expression) promoters [ 128 ]. When these promoter mutants carrying PsXEG1 (X02 and X03) or PsNLP1 (N02 and N10) were tested on Williams (susceptible) and two resistant ( Rps3b and Rps3c ) soybean cultivars, these mutants gained virulence against the resistant Rps3b cultivar while mutants containing the PsACT promoter (A24 and A26) were unable to infect soybean cultivars carrying Rps3b [ 128 ]. No infection was observed with the WT and T1 control on soybean cultivars carrying Rps3b [ 128 ].…”

“…When these promoter mutants carrying PsXEG1 (X02 and X03) or PsNLP1 (N02 and N10) were tested on Williams (susceptible) and two resistant ( Rps3b and Rps3c ) soybean cultivars, these mutants gained virulence against the resistant Rps3b cultivar while mutants containing the PsACT promoter (A24 and A26) were unable to infect soybean cultivars carrying Rps3b [ 128 ]. No infection was observed with the WT and T1 control on soybean cultivars carrying Rps3b [ 128 ]. Further transcriptomic studies with these promoter mutants highlighted a difference in gene expression in the resistant Rps3b cultivar such as the wound-inducible, jasmonate synthesis-degradation lipoxygenase (LOX-1) and the proline extensin-like receptor kinase 1 (PERK1) [ 128 ].…”

“…No infection was observed with the WT and T1 control on soybean cultivars carrying Rps3b [ 128 ]. Further transcriptomic studies with these promoter mutants highlighted a difference in gene expression in the resistant Rps3b cultivar such as the wound-inducible, jasmonate synthesis-degradation lipoxygenase (LOX-1) and the proline extensin-like receptor kinase 1 (PERK1) [ 128 ]. Compared to the WT strain, LOX-1 and PERK1 were upregulated in soybean cultivars (carrying Rps3b ) infected with the mutant with the PsACT promoter (A24) expressed, while they were downregulated in those infected with the promoter mutants, PsXEG1 (X03) and PsNLP1 (N02), respectively, at 24 hpi [ 128 ].…”