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. 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).
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. Overall design: A total of 12 soil samples were analyzed for functional genes of microbial communities. The soil samples include soil warming treatment and control with six biological replicates. Please note that the *532.exp.ftr files recorded intensities of targeted spots, and *532.void.ftr files were intensities of the areas between two adjacent targeted spots, which were used as background intensity (noise) in the normalization step in GeoChip.
Project description:We used custom Nimblegen microarrays representing whole-larval transcriptomes for two species (Papilio zelicaon [this submission] and Erynnis propertius [submitted seperately]) to assess gene expression differences affecting tolerance to climatic regimes. Many individuals were sourced from populations from the northern periphery and center of the species' (shared) range; these were each divided into groups treated under peripheral and central climate regimes, resulting in 4 experimental groups for each species (Peripheral Source, Peripheral treatment; Peripheral Source, Central Treatment; Central Source, Peripheral Treatment; Central Source, Central Treatment). Using technical microarray replicates allowed us to use ANOVA to identify genes whose expression may underlie local adaptation to climate (i.e., those showing an interaction term between source and population). Abstract: Population differences may determine geographic range shifts and adaptive evolution under climate change. Local adaptation in peripheral populations could preclude or slow range expansions, and populations with different genetic make-up could have distinct trajectories that produce complex spatial patterns of population change. To investigate the genetic extent of local responses to climate change, we exposed poleward-periphery and central populations of two Lepidoptera to reciprocal, common-garden climatic conditions and compared whole-transcriptome expression. We found significant expression differences between populations in both species. In addition, several hundred genes including genes involved in energy metabolism and oxidative stress responded in a localized fashion in the species that exhibits greater population structure and local adaptation. Expression levels of these genes are most divergent in the same environment in which we previously detected phenotypic divergence in metabolism. By contrast, we found no localized genes in the species with higher gene flow, reflecting the lack of previously observed local adaptation. These results suggest that population differences do not generalize easily, even for related species living in the same climate, but some taxa deserve population-level consideration when predicting the effects of climate change. Previously we sequenced and assembled whole larval transcriptome ESTs sourced from pooled central-population individuals subjected to environmental stressors (see O'Neil et al., 2008). From these assemblies custom Nimblegen microarrays were designed (Nimblegen, Inc.), representing 34,609 putative gene sequences for E. propertius (submitted separately) and 25,735 putative gene sequences for P. zelicaon (this submission). Probe designs sought 5 representative 60mer probes for E.propertius and 4 representative probes for P. zelicaon. Messenger RNA was was sampled from multiple individuals of each experimental group and pooled before being converted to cDNA and hybridized to technical replicate microarrays. Three technical replicates for each experimental group were used, for a total of 12 microarrays (per species). Microarray data were log2 transformed and quintile-normalized (Bolstad et al. 2003) on a per-species basis.