| 研究実績の概要 |
In FY2013, we identified new metabolic markers of herbivory in rice. In FY2014, we established that these compounds (p-coumaroylputrescine, CoP and feruloylputrescine, FP) also accumulate in isolated rice cells treated with crude oral secretions (OS) from rice herbivores. FP-guided bioassays were used for partial purification of putatively novel elicitor activity from Mythimna loreyi (MYL) OS, which was different from the function of fatty acid-amino acid conjugates (FACs). Synergistic effect between FACs and novel elicitor was found. Although FACs were not detected in rice specialist herbivore P. guttata OS, a putative novel elicitor, likely corresponding to MYL activity, was sufficient for FP and momilactone accumulations in rice cells. At present, we pursue complete structural elucidation of the novel elicitor. In addition, the flux and initiation of JA biosynthesis in rice plants was established. We used homogenized rice leaves to show that enzyme components for JA biosynthesis are constitutively present in rice cells. The flux into the pathway is then controlled by α-linolenic acid availability/release from cell membranes upon wounding. The complete JA pathway leading to JA and JA-Ile biosynthesis was only operational in intact tissues, while the activity in disrupted rice cells was limited to accumulation of JA intermediate, OPDA. These findings are important for connecting novel elicitor activity to innate responses, such as hormone and phytoalexin accumulations in rice.
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