Genome-wide transcriptional changes triggered by water deficit on a drought-tolerant common bean cultivar
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ABSTRACT: Common bean (Phaseolus vulgaris L.) is a relevant crop cultivated over the world, largely in water insufficiency vulnerable areas. Since drought is the main environmental factor restraining worldwide crop production, efforts have been invested to amend drought tolerance in commercial common bean varieties. However, scarce molecular data are available for those cultivars of P. vulgaris with drought tolerance attributes. As a first approach, Pinto Saltillo (PS), Azufrado Higuera (AH), and Negro Jamapa Plus (NP) were assessed phenotypically and physiologically to determine the outcome in response to drought on these common bean cultivars. Based on this, a Next-generation sequencing approach was applied to PS, which was the most drought-tolerant cultivar to determine the molecular changes at the transcriptional level. The RNA-Seq analysis revealed that numerous PS genes are dynamically modulated by drought. In brief, 1005 differentially expressed genes (DEGs) were identified, from which 645 genes were up-regulated by drought stress, whereas 360 genes were down-regulated. Further analysis showed that the enriched categories of the up-regulated genes in response to drought fit to processes related to carbohydrate metabolism (polysaccharide metabolic processes), particularly genes encoding proteins located within the cell periphery (cell wall dynamics). In the case of down-regulated genes, heat shock-responsive genes, mainly associated with protein folding, chloroplast, and oxidation-reduction processes were identified. Our findings suggest that secondary cell wall (SCW) properties contribute to P. vulgaris L. drought tolerance through alleviation or mitigation of drought-induced osmotic disturbances, making cultivars more adaptable to such stress. Altogether, the knowledge derived from this study is significant for a forthcoming understanding of the molecular mechanisms involved in drought tolerance on common bean, especially for drought-tolerant cultivars such as PS.
Project description:Common bean (Phaseolus vulgaris L.) is an important crop both as a source of protein and other nutrients for human nutrition and as a nitrogen fixer that benefits sustainable agriculture. This crop is affected by halo blight disease, caused by the bacterium Pseudomonas syringae pv. phaseolicola (Pph), which can lead to 45% yield losses. The resistance of common bean to Pph is conferred by six loci (Pse-1 to Pse-6) and minor-effect quantitative trait loci (QTLs); however, information is lacking on the molecular mechanisms implicated in this pathosystem. Here, we describe an in-depth RNA-sequencing analysis of the tolerant G2333 bean line in response to the Pph strain NPS3121. We identified 275 upregulated and 357 downregulated genes in common bean in response to Pph infection. These differentially expressed genes were mapped to all 11 chromosomes of P. vulgaris. The upregulated genes were primarily components of plant immune responses and negative regulation of photosynthesis, with enrichment for leucine-rich repeat (LRRs) and/or malectin-like carbohydrate-binding. Interestingly, LRRs and malectin genes mapped to same location as previously identified Pph resistance loci or QTLs. For instance, the major loci Pse-6/HB4.2 involved in broad-resistance to many Pph races, co-located with induced LRR-encoding genes on Pv04. These findings indicate a coordinated modulation of genes involved in pathogen perception and signal transduction. In addition, the results further support these LRR/malectin loci as resistance genes in response to halo blight. Thus, these genes are potential targets for future genetic manipulation, enabling the introduction of resistance to Pph into elite cultivars of common bean.
Project description:Drought is one of the main climate threats for crop plant production limitation. Climate change models predict constant global warming accompanied by strong reduction in water availability, especially for agricultural needs. Potato belongs to crop plants that are considered as sensitive to water shortage. Global estimation analyses show that drought may decrease potato yield by 18-32% in the period of 2040-2069 (Hijmans, 2003, Obidiegwu et al. 2015, Front in Plant science). Crop models predict that potato yields may reduce by ~30% as a result of water deficit in Poland (http://www.climateadaptation.eu/poland/agriculture-and-horticulture/). Genetic variability between potato cultivars has been described regarding their tolerance to drought (Soltys-Kalina et al. 2016). To diminish the effect of forecasted potato harvest losses, it is crucial to identify as many as possible potato plant strategies to withstand long drought periods during vegetative season. For this reason, we decided to analyse the expression differences in transcriptomes independently in two selected pairs of potato cultivars, Gwiazda/Oberon and Tajfun/Owacja. Cultivars in each pair are closely related to each other (having one parent in common or one grandparent in common, respectively) but differ in their sensitivity to drought conditions. In this paper, we identified at least 24 top selected genes whose expression profiles differ significantly during drought period when closely related studied cultivars are compared. Moreover, all but one of selected potato genes have their homologues in Arabidopsis plant genome. We found that A. thaliana mutants with mostly downregulated expression of seven selected homologous genes differ in their response to drought. To our knowledge, all of these genes were until now not reported as drought-related. Thus, our original approach and obtained results allowed to identify new players in plant response to drought.
Project description:Effective weed management tools are crucial for maintaining the profitable production of snap bean (Phaseolus vulgaris [L.]). Preemergence herbicides help the crop to gain a size advantage over the weeds, but the few preemergence herbicides registered in snap bean have poor waterhemp (Amaranthus tuberculatus) control, a major pest in snap bean production. Waterhemp and other difficult-to-control weeds can be managed by flumioxazin, an herbicide that inhibits protoporphyrinogen oxidase (PPO). However, there is limited knowledge about crop tolerance to this herbicide. We aimed to quantify the degree of snap bean tolerance to flumioxazin and explore the underlying mechanisms. A genome-wide association mapping approach was employed, utilizing field-collected data from a snap bean diversity panel. The response to a preemergence application of flumioxazin was measured by assessing plant population density and shoot biomass variables. Snap bean tolerance to flumioxazin is associated with a single genomic location in chromosome 02. Tolerance is influenced by several factors, including those that are indirectly affected by seed size/weight and those that directly impact the herbicide's metabolism and protect the cell from reactive oxygen species induced damage. Transcriptional profiling and co-expression network analysis identified biological pathways likely involved in flumioxazin tolerance, including oxidoreductase processes. Upregulation of genes involved in those processes is possibly orchestrated by a transcription regulator located in the region identified in the GWAS analysis. Several entries belonging to the Romano class, including Bush Romano 350, Roma II, and Romano Purpiat presented high levels of tolerance in this study. The alleles identified in the diversity panel that condition snap bean tolerance to flumioxazin shed light on a novel mechanism of herbicide tolerance and can be used in crop improvement.
Project description:Drought is a major limiting constraint to faba bean production worldwide, including Tunisia. However, molecular mechanisms underlying faba bean responses to drought stress are not well understood. In this context, transcriptome analysis by RNA-seq was performed to investigate drought-related genes and construct a network of faba bean drought stress response and tolerance. De novo assembly of the transcriptome generated 26,728 differentially expressed genes (DEGs). Of these, 13,920 were up-regulated and 12,808 down-regulated in faba bean drought-stressed leaves. Moreover, a total of 10,800 simple sequence repeats (SSRs) and 2130 transcription factors involved in major metabolic pathways including abscisic acid (ABA)-dependent and -independent signaling pathway were identified. GO, KOG and KEGG enrichment analyses revealed that these DEGs were involved in several important processes including photosynthesis, flavonoid biosynthesis, response to stimulus and abiotic stress, reactive oxygen species (ROS) scavengers, signal transduction, biosynthesis of secondary metabolites and transporters, suggesting the involvement of these important pathways in faba bean response to water deficit. Various stress proteins such as late embryogenesis abundant proteins (LEA), dehydrins (DHNs) and heat shock proteins (HSPs) have been identified and their expression was robustly upregulated in drought-stressed leaves, indicating their key contribution to drought response and adaptation by conferring protection and providing stability to faba bean plant cellular processes under water deficit. The reliability of the RNA-seq results was confirmed by the analysis of 10 randomly selected genes using qRT-PCR. Taken together, these findings help advancing our knowledge and can guide breeding programs aimed at improving the tolerance of faba bean to drought stress.
Project description:Common Bacterial Blight (CBB) is a major threat to bean crops caused by Xanthomonas citri pv. fuscans (Xcf). The pathogenicity of Xcf is known to be dependent upon a functional Type 3 Secretion System (T3SS), that allows the injection of numerous Type III Effectors (T3Es) into plant cells. We generated a transcriptomic dataset to compare the response of susceptible and resistant cultivars of Phaseolus vulgaris to the inoculation of the virulent strain Xcf CFBP4885 or its avirulent T3SS-defective hrcV mutant (CFBP13802). This dataset is a valuable resource to investigate the role of T3Es in subverting the cellular functions of bean.
Project description:Purpose: To identify nucleosome-depleted regions in response to drought in the kidney bean, a genome-wide chromatin profiling strategy was implemented. A better understanding of these OCRs (Open chromatin regions) will be useful in exploring potential genomic regions for crop improvement. Results: Using a comprehensive FAIRE-Seq approach, nucleosome-free chromatin regions were explored in kidney bean (Phaseolus vulgaris. L) in response to both drought and rewatering stress. In all samples, FAIRE peaks (>50%) were enriched in the promoter regions. The drought samples showed peaks very distinct from control and rewatered samples, which showed peaks predominantly at the transcription start site (TSS). Drought and heat-responsive genes and transcription factors were identified within the flanking region of differential peaks. When drought was compared to control, it showed upregulated differential peaks primarily in the promoter and distal intergenic regions. Conclusion: By analyzing FAIRE we are able to identify distinct genomic regions corresponding to droughts and controls. Upstream regions of genes play a significant role in drought stress response. Our data suggest that promoter regions of >2 kb, downstream regions of <= 300, and distant regulatory regions are predominant during the upregulation of drought stress. It would also be helpful to note that genomic regions vary in response to drought, and distal intergenic regions may also be involved in drought responses. Understanding plant genomes and epigenomics could help us develop varieties that can withstand extreme weather conditions.
Project description:Floral organs are extremely sensitive to stress during anthesis and lead to severe yield loss. Rice anthers and pollinated pistils of two cultivars with contrasting tolerance to heat and drought stress under variable conditions, including control, heat, combined heat and drought stress, were used to explore gene expression pattern in male and female reproductive organs during anthesis under control and stress conditions. More gene regulation was induced by combined drought and heat stress than heat in anthers of both cultivars. N22 showed less regulation under combined stress than Moroberekan. The overlap of regulated genes between two cultivars was rather low, indicated the distinct molecular stress responses. We used whole genome microarrays to explore gene expression pattern and molecular mechanisms in male and female reproductive organs during anthesis under control and stress conditions in two rice cultivars, sought to identify the key transcripts that play roles in inducing heat and drought tolerance during reproduction in rice.
Project description:Wheat cultivars ‘TAM 111’ and ‘TAM 112’ have been dominantly grown in the Southern U.S. Great Plains for many years due to their excellent, yet variable, drought tolerance. To identify the molecular basis and genetic control of drought tolerance in these two landmark cultivars, RNA-seq analysis was conducted to compare gene expression difference in flag leaves under fully irrigated (wet) and water deficient (dry) conditions. Of the 122,017 gene sequences assembled, 2,254 genes showed significantly altered expression patterns under dry and wet conditions in the two cultivars. TAM 111 had 593 and 1,532 dry-wet differentially expressed genes (DEGs), and TAM 112 had 777 and 1,670 at heading and grain-filling stages, respectively. The two cultivars have 1,214 (53.9%) dry-wet DEGs in common, which agreed with their excellent adaption to drought, but 438 and 602 dry-wet DEGs were respectively shown only in TAM 111 and TAM 112 suggested that each may have a specific mechanism to cope with drought. Annotation of all 2,254 genes with dry-wet expression difference found 1,855 have functions related to biosynthesis, stress responses, defense responses, transcription factors and cellular components related to ion or protein transportation and signal transduction. Comparing hierarchical structure of biological processes, molecule functions and cellular components revealed the significant regulation differences between TAM 111 and TAM 112, particularly for genes of phosphorylation and adenyl ribonucleotide binding, and proteins located in nucleus and plasma membrane. Comparing gene expressions involved in responses to stresses of water deprivation, heat and oxidative, ABA-induced signal pathway and transcription regulation found TAM 112 have more specific dry-wet DEGs than TAM 111 with most of them up-regulated, indicating that TAM 112 is more active than TAM 111 in response to drought. In addition, 399 dry-wet DEGs with unknown functions included 258 genes encoding predicted uncharacterized proteins and 141 unannotated genes with no similar sequences identified in the databases. These may represent novel genes related to drought response in TAM 111 or TAM 112. This research thus revealed different drought-tolerance mechanisms in TAM 111 and TAM 112 and identified useful drought tolerance genes for wheat adaption.