Accumulation of Tryptamine in Barley Leaves Irradiated with UV Light

Abstract

Tryptamine was identified as a stress compound in UV -irradiated barley leaves. Its induction was also observed to occur upon the inoculation of plant pathogenic fungi. In the interaction between barley and powdery mildew fungus, the induction was related to the degree of resistance and spore germination was inhibited by tryptamine in vitro, suggesting that it acts as a defense substance.Plants have various kinds of defense reactions against attacks by pathogens. In barley (Hordeum vulgare L.), geneticallydetermined resistance has been observed against powdery mildew fungus, Erysiphe graminis f. sp. hordei 1 -3) but its chemical or biochemical basis is still not well understood. Pathological defense responses in plants are often reproduced by abiotic stresses, such as UV irradiation and mechanical injuries. Therefore the examination of these stress responses is expected to give some clue for elucidating the metabolic changes upon the infection by pathogens. Here we report the identification of a stress substance in barley leaves produced after UV irradiation, together with the quantitative analyses of its production in terms of the biological interaction between barley leaves and pathogenic fungi.Two-week-old barley seedlings (cv. Minorimugi) were UV irradiated for 10min using a Toshiba germicidal tube GL-15 at an approximate distance of 20 cm. Irradiated seedlings were grown for 24 h at 25°C and the leaves were detached to be extracted with MeOH. Changes in the constituent profile were surveyed by gradient HPLC (column, Cosmosil 5ClS-AR, 4.5 x lS0mm; solvent, starting with 20% MeOH in water containing 0.1 % H 3 P0 3 for S min, then linearly increasing the concentration of MeOH to SO% in 25 min; flow rate, O.S ml/min; detection, fluorescence emission at 410 nm with the excitation at 290 nm) and a marked increase of a fluorescent substance (t R S.7 min) was observed in the extract from the UV-irradiated leaves compared to that from the control.To characterize this fluorescent substance, irradiated leaves (420 g) were extracted with 80% MeOH and the extract was concentrated in vacuo to be partitioned between EtOAc and water. The aqueous phase was then purified by two steps of preparative HPLC (column, Cosmosil SClS-AR, 20 x 2S0mm; solvents, 20% MeOH in water containing 0.1 % TFA (1st) and 15 0 ft) CH 3 CN in water containing 0

Accumulation of Indole‐3‐Acetic Acid in Rice sl Mutant Leaves Infected with Bipolaris oryzae

“…hordei induced tryptamine production in barley (Miyagawa et al. ), and treatment with JA induced 2‐phenylethylamine in buckwheat (Horbowicz et al. ).…”

“…hordei (Miyagawa et al. ). We also found that serotonin was inhibitory to hyphal growth of B. oryzae .…”

“…Infection of powdery mildew fungus Erysiphe graminis f.sp. hordei induced tryptamine production in barley (Miyagawa et al 1994), and treatment with JA induced 2-phenylethylamine in buckwheat (Horbowicz et al 2015). An increase in methoxytyramine content was demonstrated in onion epidermis challenged with Botrytis allii (McLusky et al 1999).…”

Indole‐related Compounds Induce the Resistance to Rice Blast Fungus, Magnaporthe grisea in Barley

“…Furthermore, it was demonstrated that the accumulation of tryptamine caused by TDC gene activation inhibited sweet potato whitefly ( Bemisia tabaci ) reproduction on transgenic tobacco plants (Thomas et al., 1995). In barley, it was demonstrated that tryptamine accumulated in the seedlings by mechanical and biological stress (Miyagawa et al., 1994; Matsuo et al., 2001). These studies suggest that tryptamine pathway‐related compounds may play an important role in disease resistance of plants.…”

Indole derivatives enhance resistance against the rice blast fungus Magnaporthe oryzae

“…In barley, tryptamine accumulated in seedlings in response to mechanical and biological stress (Matsuo et al 2001;Miyagawa et al 1994). These studies suggested that indole derivatives may play an important role in plant disease resistance.…”