Differential Expression Pattern of Pathogenicity-Related Genes of Ralstonia pseudosolanacearum YQ Responding to Tissue Debris of Casuarina equisetifolia

Abstract

Ralstonia solanacearum species complex (RSSC) contains a group of destructive plant pathogenic bacteria, causing bacterial wilt of over 200 species of crops and trees, such as Casuarina equisetifolia, worldwide. RSSC can survive in the soil environment for a long time and start infection after activated by host plants. This study conducted a transcriptome analysis on the expression pattern of the pathogenicity-related genes of a new isolated RSSC strain YQ (Ralstonia pseduosolanacearum phylotype I-16) in response to C. equisetifolia cladophyll (a branch of a stem that resembles and functions as a leaf) and root debris under in vitro culture. The cladophyll debris induced more genes upregulated than the root debris, including pathogenicity-related genes involved in motility, effectors, type III secretion systems, quorum sensing, and plant cell wall degradation. Besides, many differentially expressed genes were related to transcriptional regulator such as cyclic dimeric guanosine monophosphate. Moreover, the cultures with cladophyll debris induced a faster wilting in bioassays, and the cell swimming was enhanced by cladophyll exudate. C. equisetifolia cladophylls could activate the expression of pathogenicity-related genes of strain YQ and accelerate infection. Our findings suggest that litterfall management in C. equisetifolia forests, or even other plantations, should receive attention to prevent the induction of bacterial wilt disease caused by RSSC.

Gene expression changes throughout the life cycle allow a bacterial plant pathogen to persist in diverse environmental habitats

“…H-NS also silences DNA acquired through horizontal gene transfer, such as pathogenicity islands [65][66][67]. In harmony with this, expression of most genes associated with host virulence was repressed in soil (Table 1 and S4 Fig), as observed in other soil-borne pathogens [68] and R. solanacearum exposed to plant debris present in soil [69]. Since R. solanacearum is naturally competent, the induction of H-NS expression may act as a sentinel mechanism preventing uncontrolled expression of newly acquired DNA foreign DNA from the soil microbiome.…”

“…In harmony with this, expression of most genes associated with host virulence was repressed in soil ( Table 1 and S4 Fig ), as observed in other soil-borne pathogens [ 68 ] and R . solanacearum exposed to plant debris present in soil [ 69 ]. Since R .…”

Transcriptional alterations of the resistant potato genotype ‘Cruza 148’ in response to Ralstonia solanacearum infection

“…R. solanacearum being a soil‐inhabiting organism, the initial attraction of the bacteria to host plants and the attack on the root system are critical steps in the spread of the disease that should receive critical attention. The pathogen enters the plant by penetrating wounds on the roots and quickly invades the xylem tissue, generating enormous quantities of exopolysaccharides that disrupt the water movement and ultimately lead to plant death (Duan et al., 2018; Zhou et al., 2021). The phytopathogen is dispersed through water, soil or infected planting material (Abdurahman et al., 2019; Álvarez et al., 2010; Khokhani et al., 2018).…”

“…Besides identifying and mapping disease‐resistant quantitative trait loci, the response of the roots of diverse plant species to R. solanacearum infection has also been investigated using RNA‐seq (Pan et al., 2021; Zhou et al., 2021). In various stages of infection , Ralstonia activates a number of virulence factors to enhance the progression of the disease.…”