Abstract
We previously reported that bacterial LPS acts as a potent elicitor to induce defense responses in rice cells1). We also found that the pretreatment of rice cells with a low concentration of LPS induced "primed state" for following chitin elicitation. Recent studies on the latter phenomenon, including simultaneous treatment of rice cells with both elicitors, indicated that the phenomenon should rather be interpreted as a synergistic effect of these elicitors.
To confine the structure required for the biological activities of LPS in rice, we first examined the activity of LOS, a smaller molecule consisting of a defined oligosaccharide unit and Lipid A2). LOS induced defense responses and synergistic effects in rice cells as similar to the whole LPS molecules. Examination of the biological activities of Lipid A and oligosaccharide obtained by mild acid hydrolysis of LOS showed that the Lipid A induced both responses in the rice cells but the remaining portion, oligosaccharide fraction, did not. These results clearly showed that rice cells recognize LPS through the Lipid A structure.
1)Desaki et al., Plant Cell Physiol., 47, 1530 (2006). 2)Alba et al., ChemBioChem, 9, 896 (2008).
