A research team has meticulously analyzed the transcriptional response of Impatiens walleriana to Plasmopara obducens infection, revealing between 3,000 and 4,500 differentially expressed transcripts at various stages of the disease.


Source: André Karwath aka Aka

Bizzy Lizzy plant (Impatiens walleriana)

Through this study, published in Ornamental Plant Research, they have constructed a de novo transcriptome assembly that identified key genes involved in the plant susceptibility, including several stress response genes, receptor-like kinases (RLKs), and resistance genes. This investigation not only enhances our understanding of the molecular interactions between I. walleriana and its pathogen, but also provides a fundamental resource for future efforts to engineer disease resistance in this economically significant ornamental crop.

Severe threat

Downy mildews, including impatiens downy mildew (IDM), pose severe threats to both agronomic and ornamental crops, significantly impacting industries like floriculture. The pathogen, Plasmopara obducens, is a recent emergence and has had a major economic impact since it was first detected in cultivated Impatiens walleriana in the United States in 2004. Current research has begun to unravel the genomic basis of the host and pathogen, yet gaps remain in understanding the complete host-pathogen interactions and developing IDM-resistant cultivars.

The study dives into the transcriptome analysis of I. walleriana during its infection by P. obducens, aiming to pinpoint candidate genes linked to susceptibility. This research is pivotal in guiding future breeding efforts to enhance resistance against IDM, responding to strong consumer demand for robust I. walleriana cultivars.

In this study, RNA-Seq and de novo transcriptome assembly were utilized to examine transcriptional changes in I. walleriana during infection with P. obducens. A total of 528,964,774 clean reads were used to construct a de novo assembly, resulting in 73,022 optimized contigs. Differential expression analysis identified 3,000 to 4,500 differentially expressed transcripts  (DETs) across various infection stages.

Several receptor-like kinases (RLKs), resistance genes, powdery mildew susceptibility genes, transcription factors (including grape downy mildew susceptibility factor), retrotransposons, and many other plant stress-related genes were predominantly differentially expressed in I. walleriana in response to P. obducens. Functional annotation and gene set enrichment analysis indicated activation and deactivation of numerous stress-responsive genes throughout the infection cycle, highlighting the significant transcriptional reprogramming in I. walleriana in response to the pathogen.

Host-pathogen interactions

According to the study’s lead researcher, Prof. Gul Shad Ali, “ Our research focused on transcriptome analysis of I. walleriana during compatible interaction with P. obducens. These results could provide insights and lay the groundwork for future studies in understanding both host-pathogen interactions in IDM.”

This study not only offers insights into the susceptibility mechanisms of I. walleriana to P. obducens, but also provides a robust foundation for future research aimed at enhancing downy mildew resistance, thus potentially restoring the ornamental value of impatiens affected by this devastating disease.