GSE173535
Pseudomonas phaseolicola preferentially modulates genes encoding leucine rich repeat and malectin domains in the bean landrace G2333
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. Overall design: Fully expanded primary leaves of the bean genotype G2333 were syringe-infiltrated with bacterial inoculum or water as a mock control. After inoculation, plants were grown under the same conditions as described below until the time of sampling. Leaflets from the same plant were collected at each time point, 6 and 12 hours post inoculation (hpi), flash frozen in liquid nitrogen, and stored at -80°C until processing. Leaves collected at 6 and 12 hpi were pooled for total RNA extraction, and RNA from two different plants were pooled for RNA sequencing. The experiment was repeated twice, resulting in four biological replicates.