Extensin over‐expression in Arabidopsis limits pathogen invasiveness

Abstract

SUMMARY The function of the cell wall protein extensin has been the subject of much speculation since it was first isolated over 40 years ago. In order to investigate the role of extensins in plant defence, we used the gain-of-function strategy to generate transgenic Arabidopsis plants over-expressing the EXT1 extensin gene. These were infected with the virulent bacterial pathogen Pseudomonas syringae DC3000 and symptom development was monitored. Lesions on the transgenics were on average five-fold smaller than those on the wild-type, did not increase in area over the time period of infection, accumulated a small bacterial load and showed very little chlorosis outside the lesion boundary. By contrast, lesions on the wild-type were large, spread to over 50% of the leaf area, continued to increase in size over the time course of the infection, accumulated a bacterial load 100-fold higher than that found in the transgenics, and showed a large chlorotic area outside the lesion boundary. SEM of lesions showed no evidence of bacteria at the lesion boundary in the extensin-over-expressing transgenics, whereas bacteria were always seen at the lesion boundary on the wild-type. Analysis of transgenics carrying an EXT1-GUS promoter-reporter fusion showed expression of GUS in a ring around the boundary of the lesion. Basal defences and signal transduction pathways involved in plant defence were not perturbed in the transgenics, as shown by the analysis of the expression of PR1 and PDF1.2 genes. These results show that extensin over-expression limits pathogen invasiveness.

Tomato Transcriptional Changes in Response toClavibacter michiganensissubsp.michiganensisReveal a Role for Ethylene in Disease Development

“…The up-regulation of two extensin genes, which were categorized in the cell-wall-related category, is also consistent with a defense function. Extensins are, in fact, Hyp-rich glycoproteins that are hypothesized to form cross-linked networks that strengthen the plant cell wall, and so create a barrier to pathogen attack (Wei and Shirsat, 2006). A significant number of genes related to the production and neutralization of reactive oxygen species were found to be up-regulated in this study.…”

Over-expression of snakin-2 and extensin-like protein genes restricts pathogen invasiveness and enhances tolerance to Clavibacter michiganensis subsp. michiganensis in transgenic tomato (Solanum lycopersicum)

“…The antimicrobial peptides SN1 and SN2 from potato and the cell wall-associated protein extensin have been previously implicated in resistance to bacterial diseases (Berrocal-Lobo et al 2002;Wei and Shirsat 2006;Almasia et al 2008). Using virus-induced gene Fig.…”

“…Research on a number of host-pathogen systems has shown that extensin levels increase in response to pathogen ingress and proliferation (Davies et al 1997;Hauck et al 2003). One study convincingly demonstrated a functional linkage between extensin synthesis and plant resistance to pathogen attack (Wei and Shirsat 2006), as EXT1 over-expressing transgenic Arabidopsis were resistant to Pseudomonas syringae pv. tomato DC3000.…”

N-Acyl-Homoserine Lactone Primes Plants for Cell Wall Reinforcement and Induces Resistance to Bacterial Pathogens via the Salicylic Acid/Oxylipin Pathway

“…Both are structural components of plant cell walls and belong to the hydroxyproline-rich glycoprotein superfamily. Cross-linking of hydroxyproline-rich glycoproteins and glycosylation are key processes in the strengthening of the cell wall and contribute to plant resistance by limiting pathogen invasion (Wei and Shirsat, 2006). In addition, several other genes involved in the modification of polysaccharides were differentially regulated (AT4G25820, AT428850, AT5G5730).…”

“…The plant cell wall is a dynamic arrangement of proteins, sugars, and phenols with a substantial structural complexity that plays an essential role in plant defense (Hückelhoven et al, 1999;Wei and (E) Assessment of temperature via infrared light images in leaves of plants treated as described in (A) and exposed to Pst bacteria for 24 h. Shirsat, 2006;Hückelhoven, 2007;Deepak et al, 2010). Previously, we observed enhanced formation of papillae in barley plants pretreated with oxo-C14-HSL and challenged with the pathogenic fungus Blumeria graminis f sp hordei (Schikora et al, 2011).…”