Study : Rice plants exhibiting bacterial blight resistance at high temperature suppress abiotic response


Rice plants exhibiting bacterial blight resistance at high temperature suppress abiotic response
Background: Plant disease is a major challenge to agriculture worldwide, and it is often exacerbated by abiotic environmental factors. During some plant-pathogen interactions, heat stress increases host susceptibility, a tendency which could spell disaster in light of the global warming trends associated with climate change. Despite the importance of this phenomenon, little is known about the molecular mechanisms that cause it. To better understand host plant responses during simultaneous heat and pathogen stress, we conducted a transcriptomics experiment for rice plants infected with Xanthomonas oryzae (Xo), an economically important bacterial pathogen of rice, during high temperature stress. Results: Using RNA-Seq technology, 8,499 differentially expressed genes were identified as temperature responsive in one rice cultivar, IRBB61, experiencing susceptible and resistant interactions with Xo across three time points. Many genes with gene ontology terms associated with stress response were identified. Notably, genes in the plant hormone abscisic acid (ABA) biosynthesis and response pathways were identified as upregulated by high temperature in both mock-treated plants and plants in the susceptible interaction and suppressed by high temperature in plants in the resistant interaction. A DNA sequence motif similar to known ABA-responsive cis-regulatory elements was identified in the promoter region upstream of genes upregulated in susceptible but downregulated in resistant interactions. Conclusions: The results of our study suggest that the plant hormone ABA is an important node for cross-talk between plant transcriptional response pathways to high temperature stress and pathogen attack. Genes in this pathway represent an important focus for future study to determine how plants evolved to deal with simultaneous abiotic and biotic stresses. Overall design: RNA-Seq analysis of leaves from rice variety IRBB61 infiltrated with water at normal and high temperature regimes at 6 h post-infiltration, and rice leaves inoculated with Xanthomonas oryzae strain X11-5A carrying either an empty vector plasmid or a plasmid encoding the effector avrXa7 under normal and high temperature regimes over a time course (3, 12, 24 h post-inoculation).


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