Plant root transcriptome profiling reveals a strain-dependent response during Azospirillum-rice cooperation

Area of Science:

• Plant Science
• Microbiology
• Genomics

Background:

• Plant Growth-Promoting Rhizobacteria (PGPR) enhance plant growth and health.
• Limited understanding of how PGPR affect plant gene expression, especially phytostimulating rhizobacteria.
• Investigating the impact of Azospirillum inoculation on rice root gene expression.

Purpose of the Study:

• Identify genes regulated in rice roots after Azospirillum inoculation.
• Explore strain-specific interactions between Azospirillum and rice cultivars.
• Determine potential molecular markers for Azospirillum-rice interactions.

Main Methods:

• Genome-wide microarray analysis of rice (Oryza sativa japonica) cultivars Cigalon and Nipponbare.
• Inoculation with specific Azospirillum strains (A. lipoferum 4B and Azospirillum sp. B510).
• Comparison of gene expression profiles between inoculated and non-inoculated plants.

Main Results:

• 7384 genes (approx. 16% of total) were significantly regulated upon Azospirillum inoculation.
• 34 genes, including a PR10 ortholog, were commonly regulated by both strains, suggesting interaction markers.
• 83% of regulated genes showed strain- or combination-specific expression patterns.
• Genes involved in primary metabolism, transport, transcription, and protein fate were predominantly affected.
• Endophytic strain B510 repressed more defense-related genes than strain 4B.
• Rice genotype significantly influenced root gene expression.

Conclusions:

• Rice exhibits strain-dependent transcriptional responses to Azospirillum inoculation.
• Commonly regulated genes may serve as markers for Azospirillum-rice interactions.
• Azospirillum inoculation impacts primary metabolism, transport, and signaling pathways.
• Strain B510's endophytic nature correlates with broader repression of defense genes.
• Host genotype and complex hormone signaling networks (auxin, ethylene) mediate Azospirillum-rice cooperation.