Galactinol is a signaling component of the induced systemic resistance caused by Pseudomonas chlororaphis O6 root colonization.

Root colonization by Pseudomonas chlororaphis O6 in cucumber elicited an induced systemic resistance (ISR) against Corynespora cassiicola. In order to gain insight into O6-mediated ISR, a suppressive subtractive hybridization technique was applied and resulted in the isolation of a cucumber galactinol synthase (CsGolS1) gene. The transcriptional level of CsGolS1 and the resultant galactinol content showed an increase several hours earlier under O6 treatment than in the water control plants following C. cassiicola challenge, whereas no difference was detected in the plants without a pathogen challenge. The CsGolS1-overexpressing transgenic tobacco plants demonstrated constitutive resistance against the pathogens Botrytis cinerea and Erwinia carotovora, and they also showed an increased accumulation in galactinol content. Pharmaceutical application of galactinol enhanced the resistance against pathogen infection and stimulated the accumulation of defense-related gene transcripts such as PR1a, PR1b, and NtACS1 in wild-type tobacco plants. Both the CsGolS1-overexpressing transgenic plants and the galactinol-treated wild-type tobacco plants also demonstrated an increased tolerance to drought and high salinity stresses.

Isolation and characterization of antifungal substances from Burkholderia sp. culture broth.

A new antagonistic Burkholderia strain, designated MP-1 and producing antifungal activities against various filamentous plant pathogenic fungi, was isolated from the rhizoshere in the Naju area. Cultural characteristic studies strongly suggested that this strain belongs to the genus Burkholderia. The nucleotide sequence of the 16S rRNA gene (1491 pb) of strain MP-1 exhibited close similarity (99% to 100%) with other Burkholderia 16S rRNA genes. Extraction of fermentation broth of Burkholderia sp. MP-1 and various separations and purification steps led to isolation of four pure active molecules. The chemical structure of these four compounds-named phenylacetic acid, hydrocinnamic acid, 4-hydroxyphenylacetic acid, and 4-hydroxyphenylacetate methyl ester-was established on the basis on their gas chromatography-electron impact-mass spectrometry (GC-EI-MS) and trimethylsilation GC-EI-MS data. The four isolated compounds inhibited filamentous fungal growth on potato dextrose agar medium supplemented with 100 mg/L of phenylacetic acid, hydrocinnamic acid, 4-hydroxyphenylacetic acid and 4-hydroxyphenylacetate methyl ester individually.

2-ketogluconic acid production and phosphate solubilization by Enterobacter intermedium.

Enterobacter intermedium, isolated from grass rhizosphere, exhibited a strong ability to solubilize insoluble phosphate. This bacterium oxidized glucose to gluconic acid and sequentially to 2-ketogluconic acid (2-KGA), which was identified using HPLC and GC-MS. The ability of E. intermedium to solubilize phosphate and produce 2-KGA produce in broth medium containing different components was monitored with air and without air supply. With an air supply, the production of 2-KGA markedly increased to about 110 g/l at day 10 in media containing 0.2 M gluconic acid, while it was about 65 g/l without gluconic acid addition. With an air supply, the concentration of soluble phosphate significantly decreased to 200-250 mg/l in media containing 1% CaCO3, whereas it was about 1000 mg/l without CaCO3 addition. Without an air supply, the concentration of 2-KGA and phosphate were negligible throughout the culture period.