Project description: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.
Project description:The response of soil microbial community to climate warming through both function shift and composition reorganization may profoundly influence global nutrient cycles, leading to potential significant carbon release from the terrain to the atmosphere. Despite the observed carbon flux change in northern permafrost, it remains unclear how soil microbial community contributes to this ecosystem alteration. Here, we applied microarray-based GeoChip 4.0 to investigate the functional and compositional response of subsurface (15~25cm) soil microbial community under about one year’s artificial heating (+2°C) in the Carbon in Permafrost Experimental Heating Research site on Alaska’s moist acidic tundra. Statistical analyses of GeoChip signal intensities showed significant microbial function shift in AK samples. Detrended correspondence analysis and dissimilarity tests (MRPP and ANOSIM) indicated significant functional structure difference between the warmed and the control communities. ANOVA revealed that 60% of the 70 detected individual genes in carbon, nitrogen, phosphorous and sulfur cyclings were substantially increased (p<0.05) by heating. 18 out of 33 detected carbon degradation genes were more abundant in warming samples in AK site, regardless of the discrepancy of labile or recalcitrant C, indicating a high temperature sensitivity of carbon degradation genes in rich carbon pool environment. These results demonstrated a rapid response of northern permafrost soil microbial community to warming. Considering the large carbon storage in northern permafrost region, microbial activity in this region may cause dramatic positive feedback to climate change, which is important and necessary to be integrated into climate change models.