Real time RT-PCR expression analysis of syrB and sypA genes in the interaction between P. syringae biocontrol strains and P. digitatum
Scuderi G, Panebianco S and Cirvilleri G
Program and Abstracts, 11th International Citrus Congress (ISC Congress), 26-20 October 2008, Wuhan, China. 333 pages.
2008
บทคัดย่อ
Some strains of Pseudomonas syringae van Hall are effective in controlling postharvest diseases of citrus fruits, and their antagonistic activity has been correlated with the production in vitro of lipodepsipeptides. Syringomycin (syr) and syringopeptin (syp) lipodepsipeptides are produced through a nonribosomal peptide synthetase system, and syr-sypgenes are subjected to coordinated control by SalA and SyrF in response to environmental signals such as nutrient availability and presence of plant signal molecules. In the present study, the expression of syringomycin (syrB1) and syringopeptin (sypA) synthetase genes from seven antatgonistic P. syringae strains was evaluated in vitro on different culture media and in vivo on citrus fruits during the interaction with P. digitatum. The relative transcript level was evaluated by real-time RT-PCR one-step using the 16S rRNA as housekeeping gene. Expression analyses revealed that syrB1 and sypA genes can be differentially expressed under induced and non-induced conditions. A basal level of syrB1 gene expression was detected when P. syringae strains were grown on NB or PDB (no-induced) media. Similar results were reported for the syringopeptin synthetase gene sypA. Both genes were more actively expressed when bacteria were grown on orange peel extract media (induced) as compared to NB and PDB culture conditions. The presence of P. digitatumduring P. syringae growth on PDB, on orange peel extract and in vivo on citrus fruits resulted to be strongly stimulatory only to syrB1 expression, suggesting that at least syrB1 gene is involved in biocontrol activity. Such up-regulation was correlated with inhibition of conidial germination in vitro and with antagonistic activity in vitro and in vivo. This is the first example of monitoring expression of syrB-sypA genes in interactions between P. syringaebiocontrol agents and pathogen P. digitatum in vitro and in vivo.