LOCALIZATION OF PANTOEA AGGLOMERANS IN GRAPEVINE TISSUES BY FLUORESCENCE IN SITU HYBRIDIZATION (FISH)

• Published in: Journal of plant pathology Vol. 91; no. 4
• Main Authors: Bulgari, D, Casati, P, Quaglino, F, Bianco, P A, Iriti, M, Faoro, F
• Format: Journal Article
• Language: English
• Published: 01.12.2009
• Subjects: Bacillus; Curtobacterium; Enterococcus; Pantoea agglomerans; Vitaceae
• ISSN: 1125-4653

Endophytes are ubiquitous endosymbionts found in all plant species studied so far. Alhough their relationship with the host is in most cases not well understood, they may benefit plants by preventing pathogen colonization through different mechanisms: competition, production of allelochemicals and induction of systemic resistance (ISR). Recently, the population of bacterial endophytes associated with grapevine leaf tissues was analyzed by both cultivation and cultivation-independent methods. Isolation of bacteria by culturing revealed the presence of members of the genera Curtobacterium, Bacillus and Enterococcus. Sequence analysis of 16S rRNA gene libraries underscored a dominance of the genus Pantoea. Previous studies emphasized the potential of P. agglomerans as a biocontrol agent against a range of plant pathogens through the secretion of antibacterial molecules and/or by the activation of plant induced systemic resistance (ISR). In this study P. agglomerans distribution in grapevine leaf tissues was assessed by fluorescence in situ hybridization (FISH). For this purpose, a probe to target bacterial 16S rDNA was labelled with a fluorophore emitting in the far-red (i.e. CY5) to avoid interference with autofluorescence of the abundant phenolic compounds present in grapevine tissues. Vibratome cut slides of leaf midribs, 70-80 mu m thick, were incubated with the probe and examined with a confocal microscope. Putative endophytes were detected mainly in phloem and xylem parenchymas. The possibility of localizing endophytic bacteria inside grapevine tissues represents a valuable aid in studying their interaction with grapevine pathogens, particularly viruses and phytoplasmas.