Poaceae (R.Br.) Barnhart, 1895

Ube, Naoki, Harada, Daiyu, Katsuyama, Yuhka, Osaki-Oka, Kumiko, Tonooka, Takuji, Ueno, Kotomi, Taketa, Shin & Ishihara, Atsushi, 2019, Identification of phenylamide phytoalexins and characterization of inducible phenylamide metabolism in wheat, Phytochemistry 167, pp. 1-9 : 5

2.5. Accumulation of 1 and 2 in major Poaceae species in response to CuCl 2 treatment

To examine the distribution of 1 and 2 accumulation in Poaceae , we treated leaves of rice, maize, oat, rye ( Secale cereale ), and barley with 1 mM CuCl 2. We extracted compounds in the leaves 72 h after treatment, and analyzed the amounts of 1 and 2 by HPLC. Compounds 1 and 2 accumulated in response to CuCl 2 treatment in barley leaves, and their amounts were 3.4 and 4.4 nmol/g fr. wt, respectively. Compounds 1 and 2 were not detected in rice, maize, oat, or rye.

2.6. Antimicrobial activities of 1 and 2

The antifungal activities of 1 and 2 against phytopathogenic fungi B. sorokiniana , F. graminearum , and Alternaria brassicicola were evaluated by inhibition of conidial germination and germ tube elongation. The concentration of 1 was not enough to examine a dose-response relationship; the assay was only performed at 1,000 μM. Compounds 1 and 2 showed inhibitory effects on the conidial germination of F. graminearum and A. brassicicola but not B. sorokiniana ( Fig. 8A and B ). Conversely, compounds 1 and 2 almost completely inhibited germ tube elongation in F. graminearum and A. brassicicola at 1,000 μM and inhibited that of B. sorokiniana by 39.5 and 48.0%, respectively ( Fig. 8C ). Compound 2 demonstrated a marked inhibitory effect on the germ tube elongation of F. graminearum and A. brassicicola , even at 10 μM ( Fig. 8D ).

The inhibitory activity of 2 against Pseudomonas syringae pv. japonica was assayed by monitoring growth in liquid culture. However, 2 did not inhibit growth, even at 1,000 μM (data not shown).

Figures

Fig. 8. Antifungal activities of 1 and 2. B. sorokiniana (Bs), F. graminearum (Fg), and A. brassicicola (Ab) conidia were incubated with 1 at 1,000 μM (A) and with 2 at various concentrations between 0 and 1,000 μM (B). White bars indicated the control values. Germination rates were determined after 8 h (for B. sorokiniana and A. brassicicola) and 6 h (for F. graminearum) incubation. Conidial germ tube elongation was measured 4 h after treatment with 1 at 1,000 μM (C) or 2 at various concentrations (D). Data are the mean and standard deviation from three independent experiments. Letters (a–d) represent significant differences at p <0.05 as measured using Tukey-Kramer tests.