Gene targeting by the TAL effector PthXo2 reveals cryptic resistance gene for bacterial blight of rice

Abstract

SUMMARYBacterial blight of rice is caused by the c-proteobacterium Xanthomonas oryzae pv. oryzae, which utilizes a group of type III TAL (transcription activator-like) effectors to induce host gene expression and condition host susceptibility. Five SWEET genes are functionally redundant to support bacterial disease, but only two were experimentally proven targets of natural TAL effectors. Here, we report the identification of the sucrose transporter gene OsSWEET13 as the disease-susceptibility gene for PthXo2 and the existence of cryptic recessive resistance to PthXo2-dependent X. oryzae pv. oryzae due to promoter variations of OsS-WEET13 in japonica rice. PthXo2-containing strains induce OsSWEET13 in indica rice IR24 due to the presence of an unpredicted and undescribed effector binding site not present in the alleles in japonica rice Nipponbare and Kitaake. The specificity of effector-associated gene induction and disease susceptibility is attributable to a single nucleotide polymorphism (SNP), which is also found in a polymorphic allele of OsS-WEET13 known as the recessive resistance gene xa25 from the rice cultivar Minghui 63. The mutation of OsSWEET13 with CRISPR/Cas9 technology further corroborates the requirement of OsSWEET13 expression for the state of PthXo2-dependent disease susceptibility to X. oryzae pv. oryzae. Gene profiling of a collection of 104 strains revealed OsSWEET13 induction by 42 isolates of X. oryzae pv. oryzae. Heterologous expression of OsSWEET13 in Nicotiana benthamiana leaf cells elevates sucrose concentrations in the apoplasm. The results corroborate a model whereby X. oryzae pv. oryzae enhances the release of sucrose from host cells in order to exploit the host resources.

Consumer acceptance of food crops developed by genome editing

“…With regard to on-target gene disruption via NHEJ, the potential environmental implications also require scrutiny, in particular if the gene disruption confers herbicide or disease resistance (Butler, et al 2015;Li, et al 2012;Wang, et al 2014;Zhou, et al 2015).…”

Generation of targeted mutant rice using a CRISPR‐Cpf1 system

“…Rice is the most frequently used crop species for testing and applying CRISPR‐Cas9 tools. Several agronomic traits of rice, including yield, fertility, architecture, biotic and abiotic stress response, and herbicide tolerance, have been successfully modified by targeted mutations in one or multiple major genes (Ikeda et al ., 2016; Li et al ., 2016a,b,c; Osakabe et al ., 2016; Sun et al ., 2016; Wang et al ., 2016; Xu et al ., 2014, 2016; Zhou et al ., 2015). …”

Infection byRhodococcus fasciansmaintains cotyledons as a sink tissue for the pathogen

“…oryzae indicates that this pathogen enhances the release of sucrose from the host cells by inducing expression of OsSWEET13, a member of Clade III. Targeted mutation of OsSWEET13 led to reduced pathogenesis (Zhou et al, 2015). Earlier it was shown that two other Clade III SWEETs (OsSWEET11 and OsSWEET14) were also targets of bacterial rice blight (Li et al, 2013;Streubel et al, 2013).…”