Abstract
Ralstonia solanacearum causes one of the most common soil-borne vascular diseases of diverse plant species, including many solanaceous crops such as tomato and pepper. The resulting disease, bacterial wilt (BW), is devastating and difficult to control using conventional approaches. The aim of this study was to investigate the differentially expressed genes in pepper root systems in response to infection by R. solanacearum. DNA microarray (Capsicum annuum 135K Microarray v3.0 Gene Expression platform) analyses were performed using a susceptible genotype, ‘Chilbok’, and a resistant genotype, ‘KC350’, at 3 time points (1, 3, and 6 days post inoculation). It has been identified 115 resistance-specific genes (R-response genes) and 109 susceptibility-specific genes (S-response gene), which were up-regulated in 1 genotype, but down-regulated in the other genotype. Gene Ontology (GO) analysis for functional categorization indicated that many R-response genes were related to genes that function in xyloglucan biosynthesis and cell wall organization, while S-response genes were involved in the response to stress and cell death. The expression of genes encoding xyloglucan endotransglycosylase/hydrolase (XTH) and β-galactosidase were verified by real-time RT-PCR at an early time point of R. solanacearum infection. The results supported the idea that rapidly induced XTH expression in ‘KC350’ may play an important role in the restructuring and reinforcement of the cell wall and restrict bacterial movement in xylem vessels. In addition, induced expression of β-galactosidase in R. solanacearum-infected ‘Chilbok’ implied that degradation of the cell wall structure in vascular tissues by β-galactosidase might be an important factor facilitating R. solanacearum invasion of and movement in susceptible host plants.
Highlights
Bacterial wilt (BW) caused by the soil-born bacterial pathogen Ralstonia solanacearum is one of the most prevalent plant diseases affecting hundreds of different species (Elphinstone, 2005; Hayward, 1991)
Disease assessment of sample plants In previous bioassay experiments, disease symptoms were generally observed from R. solanacearum infected pepper plants at least 14 days after inoculation in a growth chamber
It was impossible to validate the success of pathogen infection at the time of plant sampling for RNA extraction
Summary
Bacterial wilt (BW) caused by the soil-born bacterial pathogen Ralstonia solanacearum (synonym Pseudomonas solanacearum) is one of the most prevalent plant diseases affecting hundreds of different species (Elphinstone, 2005; Hayward, 1991). In the process of infection, R. solanacearum enters the host through either wounds or natural openings such as the site of secondary root emergence or the root tip, and spreads rapidly after intercellular growth throughout the vascular parenchyma and xylem elements (Wallis and Truter, 1978). The mechanisms for natural resistance to R. solanacearum are related to limited growth and the restriction of pathogen movement within the host vascular systems. Limitation of bacterial spread in vessels in a resistant tomato genotype was associated with the production of tylose, which is a general, non-specific mechanism for inhibiting vascular pathogens or abiotic stresses like drought (Grimault et al, 1994)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
