Rice SRO1a Contributes to Xanthomonas TAL Effector-mediated Expression of Host Susceptible Genes

Area of Science:

• Plant Pathology
• Molecular Plant-Microbe Interactions
• Plant Molecular Biology

Background:

• Xanthomonas species are significant crop pathogens causing substantial yield losses.
• Transcription activator-like (TAL) effectors are virulence factors secreted by Xanthomonas that manipulate host gene expression.
• The precise molecular mechanisms by which TAL effectors activate host gene transcription are not fully understood.

Purpose of the Study:

• To elucidate the role of rice SIMILAR TO RCD ONE (SRO) family proteins in TAL effector-mediated transcription.
• To investigate the interaction between TAL effectors and OsSRO proteins in plant nuclei.
• To determine the impact of OsSRO proteins on the expression of host susceptibility and defense genes.

Main Methods:

• Yeast two-hybrid or co-immunoprecipitation assays to detect protein-protein interactions.
• Transactivation assays in rice protoplasts to measure promoter activity.
• Analysis of gene expression in wild-type and ossro1a mutant rice plants.
• Quantitative real-time PCR (qRT-PCR) to assess the expression of defense-related genes.

Main Results:

• TAL effectors were shown to interact with OsSRO1a and OsSRO1b proteins within the plant nucleus.
• OsSRO1a and OsSRO1b significantly enhanced the transcriptional activation of the OsSWEET14 promoter by the TAL effector AvrXa7.
• The expression of OsSWEET14 induced by AvrXa7 was reduced in ossro1a mutants.
• Overexpression of OsSRO1a led to increased disease resistance, correlating with upregulated expression of defense genes like WRKY62 and PBZ1.
• OsSRO1a and OsSRO1b were found to enhance the transcriptional activity of WRKY45, a key regulator of WRKY62.

Conclusions:

• Rice OsSRO1a and OsSRO1b proteins play a crucial role in positively regulating transcription induced by bacterial TAL effectors.
• These OsSRO proteins modulate the expression of both susceptibility genes (e.g., OsSWEET14) and defense-related genes (e.g., WRKY62, PBZ1).
• OsSRO1a and OsSRO1b act as important mediators in the interplay between plant-pathogen interactions and host transcriptional machinery.