RNA virus-like particles in pathogenic plant trypanosomatids

Area of Science:

• Plant pathology
• Molecular biology
• Virology

Background:

• Phytomonas are trypanosomatid protozoa that can cause plant diseases.
• Hartrot disease in coconut and Marchitez sorpressiva in oil palm are economically significant plant ailments.
• The etiological agents of these diseases are not fully understood, particularly the role of potential viral or genetic factors.

Purpose of the Study:

• To investigate the presence of double-stranded RNA (ds RNA) in pathogenic Phytomonas isolates associated with coconut and oil palm diseases.
• To determine if this ds RNA is specific to pathogenic strains and potentially linked to disease causation.
• To characterize the physical nature of the ds RNA found in these isolates.

Main Methods:

• Isolation and purification of Phytomonas strains from infected coconut and oil palm plants.
• Extraction and analysis of nucleic acids, specifically double-stranded RNA (ds RNA), from Phytomonas isolates.
• Comparison of ds RNA profiles between pathogenic and non-pathogenic Phytomonas strains.
• Electron microscopy to visualize virus-like particles in fractions containing ds RNA.

Main Results:

• A double-stranded RNA (ds RNA) of approximately 4.7 kb was consistently detected in six Phytomonas isolates pathogenic to coconut and oil palm.
• This specific ds RNA was absent in ten non-pathogenic Phytomonas isolates from lactiferous plants and in insect trypanosomatids (Crithidia, Herpetomonas).
• Electron microscopy revealed virus-like particles in sucrose gradient fractions containing the 4.7 kb ds RNA.

Conclusions:

• The presence of a specific 4.7 kb ds RNA is strongly correlated with the pathogenicity of Phytomonas isolates in coconut and oil palm.
• This ds RNA is likely of viral origin, as indicated by its association with virus-like particles.
• The findings suggest a potential viral etiology for Hartrot and Marchitez sorpressiva diseases, mediated by Phytomonas.