A genome-wide association study reveals cytokinin as a major component in the root defense responses againstRalstonia solanacearum

Abstract

Bacterial wilt caused by the soil-borne pathogen Ralstonia solancearum is economically devastating, with no effective methods to fight the disease. This pathogen invades plants through their roots and colonizes their xylem, clogging the vasculature and causing rapid wilting. Key to preventing colonization are the early defense responses triggered in the host’s root upon infection, which remain mostly unknown. Here, we have taken advantage of a high-throughput in vitro infection system to screen natural variability associated to the root growth inhibition phenotype caused by R. solanacearum in Arabidopsis during the first hours of infection. To analyze the genetic determinants of this trait, we have performed a Genome-Wide Association Study, identifying allelic variation at several loci related to cytokinin metabolism, including genes responsible for biosynthesis and degradation of cytokinin. Further, our data clearly demonstrate that cytokinin signaling is induced early during the infection process and cytokinin contributes to immunity against R. solanacearum. This study highlights a new role of cytokinin in root immunity, paving the way for future research that will help understanding the mechanisms underpinning root defenses.

Solanaceous plants switch to cytokinin‐mediated immunity against Ralstonia solanacearum under high temperature and high humidity

“…We show here that CK signalling was activated to lower the susceptibility of pepper plants to RSHT treatment since the exogenous application of tZ or overexpression of CaIPT5 significantly raised the resistance of pepper plants to RSHT treatment (Figure 3). This result is consistent with that of a recently published work that cytokinin acts as a major component in the root defence responses against R. solanacearum in Arabidopsis by GWAS using 430 Arabidopsis thaliana ecotypes, which might include the influence of temperature conditions on the immunity of Arabidopsis against R. solanacearum (Alonso‐Díaz et al, 2021). Importantly, immunity mediated by CK signalling was closely linked to the upregulation of GST‐encoding genes, including Mgst3 and PRP1 (Figures 4 and 5).…”

Study of natural diversity in response to a key pathogenicity regulator of Ralstonia solanacearum reveals new susceptibility genes in Arabidopsis thaliana

“…More recently, a GWAS using an in vitro system allowing the study of A. thaliana early root phenotypes after R . solanacearum inoculation highlighted a new role for cytokinin in root immunity in response to GMI1000 (Alonso‐Díaz et al, 2021). Altogether, these results confirmed the benefit of considering different mapping populations in GWAS to unravel the genetics of complex quantitative traits (Bergelson & Roux, 2010; Brachi et al, 2013).…”

RNAi‐based genetically engineered rice resistant to black‐streaked dwarf virus does not show adverse genetic effects: A multi‐omics analysis

“…The comparisons data were profiled at the transcriptomic and metabolomic levels. Subsequently, the plant hormone signaling transduction pathway was determined to be involved in the response to external IR sequences derived from RBSDV, and the expression levels of several genes involved in this pathway were analyzed, which showed the extra positive effects of IR sequence infection derived from RBSDV, providing a reference for the unintended effects of targeting external host genes of RNAi‐based GE lines (Alonso‐Diáz et al, 2021) (Alazem & Lin, 2015). Nonetheless, it would be better to determine the specific processes underlying the interactions between siRNAs, hosts and RBSDV.…”