by led treatment on nicotiana benthamiana - SIPaV

Journal of Plant Pathology (2013), 95 (3), 477-483

Edizioni ETS Pisa, 2013

Ahn et al. 477

INHIBITING WILDFIRE AND INDUCING DEFENSE-RELATED GENE EXPRESSION BY LED TREATMENT ON NICOTIANA BENTHAMIANA S.-Y. Ahn1, S.A. Kim1, 3, K.-H. Baek2, 3 and H.K. Yun1, 3 1Department

of Horticultural Science, Yeungnam University, Gyeongsan 712-749, Korea of Biotechnology, Yeungnam University, Gyeongsan 712-749, Korea 3LED-IT Fusion Technology Research Center, Yeungnam University, Gyeongsan 712-749, Korea 2School

SUMMARY

Light plays an important role in the induction of resistance responses in various plants against diseases. In this study, the inhibition was investigated of wildfire disease caused by Pseudomonas syringae pv. tabaci in Nicotiana benthamiana in response to irradiation with light emitting diodes (LEDs) To identify the effects of various wavelengths on the induction of defense responses, N. benthamiana plants were irradiated for three days with various LEDs (380, 440, 470, and 660 nm) before and after inoculation. Symptom development showed greater suppression in response to irradiation with blue (440 nm) and red (660 nm) light than fluorescent lights. Additionally, fewer bacterial cells were recovered from the lesions of LED-treated leaves than those of fluorescent light-treated leaves. Simple LED irradiation induced the expression of defense-related genes including catalase (CAT), chalcone synthase (CHS), gluthatione-S-transferase (GST), pathogenesis-related protein (PR Q), proteinase inhibitor II (PinII), and thaumatin-like protein (TLP). Taken together, these data suggest that irradiation by LEDs could inhibit wildfire development by inducing defense responses in N. benthamiana plants. Key words: LED, pathogenesis-related proteins, resistance induction, Pseudomonas syringae pv. tabaci. INTRODUCTION

Among the various strategies used for plant disease control, the application of chemicals has been one of the most common. Because chemical treatments have a number of detrimental side effects, such as adverse consequences to human health and residual toxicity (Date et al., 2004), the development of alternative measures has been advocated for implementing human- and environmentfriendly control systems. Corresponding author: H.K. Yun Fax: +82.53.810.4659 E-mail: [email protected]

11. JPP1372RP (Yun) (ok).indd 477

It is well known that light plays an important role in the induction of resistance or defense-related responses to various pathogen attacks to plants (Diaz and Feres, 2007; Khanam et al., 2005). Since the use of eco-friendly lights with various wavelengths in the red, blue, and yellow-range wavelengths is increasing in agriculture, their effects on growth promotion and disease resistance in plants has recently been investigated (Hamamoto and Yamazaki, 2009; Hirama et al., 2007; Schuerger and Brown, 1997). Red light has been found to induce resistance in broad bean against Botrytis cinerea (Islam et al., 1998) and Alternaria tenuissima (Rahman et al., 2003) and in rice against Magnaporthe grisea (Arase et al., 2000). Tabira et al. (1989) reported that continuous irradiation with visible light at 570 nm to 680 nm protected apple leaves from Alternaria alternata apple-pathotype by inducing insensitivity to the AM-toxin, a host-specific toxin. Islam et al. (2008) demonstrated that red light induces systemic disease resistance of Arabidopsis to the root-knot nematode Meloidogyne javanica and to Pseudomonas syringae pv. tomato DC 3000. Ultraviolet (UV) light irradiation has also induced resistance to pathogens in wheat (Benedict, 1997), citrus (Chalutz et al., 1992), and grapevines (Droby et al., 1993). Upon UV light exposure, resveratrol increased in grape bunches (Cantos et al., 2000, 2001; Creasy and Coffee, 1988), grapevines (Langcake and Pryce, 1976), and peanut leaves (Rudolf and Resurreccion, 2005; Subba Rao et al., 1996). Fritzemeier and Kindl (1981) found that leaves of Vitaceae exposed to UV light stimulated the activation of stilbene synthase, which catalyzes the reaction of 4-hydroxycinnamoyl-CoA and malonyl-CoA to produce resveratrol. Light emitting diodes (LEDs) have several advantages over incandescent light sources including faster switching, lower energy consumption, improved robustness, longer lifetime, smaller size, greater durability, and reliability (Barta et al., 1992; Bula et al., 1991). Accordingly, the application of LEDs as a light source in the regulation of plant growth and photomorphogenesis has been studied in various fields (Han et al., 2000; Heo et al., 2002; Hoenecke et al., 1992; Lian et al., 2002). The production of narrow wavelength light by LED has been found to be

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Wildfire inhibition by LED treatment

Table 1. Sequences of gene-specific primers used for RT-PCR analysis. Genes Anthocyanidin synthase (ANS) Catalase (CAT) Chalcone synthase (CHS) Glutathion-S-transferase (GST) Pathogenesis-related protein (PR) Q Proteinase inhibitor II (PinII) Thaumatin-like protein (TLP)

β-actin

Primer sequences 5’-AAGGAGATTCGGGAGAAATG-3’ 5’-GCCACACTGTTCATCCTCCT-3’ 5’-GGATCCATACAAGTACCGTCC-3’ 5’-CAAGGACCCTCCAATTCTCCTG-3’ 5’-GCGACTCCTTCGAACTGTG-3’ 5’-AAGTTTTTCGGGCTTTAGGC-3’ 5’-GGCGATCAAAGTCCATGGTAG-3’ 5’-GCTTCTCCAATCCCTTAACCC-3’ 5’- CCAGAGTGACAGATATTA-3’ 5’- GCCCTGGCCGAAGTTCCT-3’ 5’-ACGATCCCATATGCACCACT-3’ 5’-TCCACTGCCCACATTACAGA-3’ 5’- GTCAACCAATGCACCTAC-3’ 5’- GGTGGATCATCCTGTGGA-3’ 5’-ACGAGAAATCGTGAGGGATG-3’ 5’-ATTCTGCCTTTGCAATCCAC-3’

very useful in investigating the effects of various wavelengths on disease resistance induction. Here, we report that LED light irradiation effectively inhibited wildfire disease lesions by Pseudomonas syringae pv. tabaci (Pst) and induced the expression of defenserelated genes in Nicotiana benthamiana. MATERIALS AND METHODS

Irradiation by LEDs with various wavelengths. N. benthamiana plants were kept in a growth room at 23°C under a 16/8 h light/dark condition for four to five weeks. The plants were placed in a black acryl box (24×50×60 cm) and irradiated under five different light sources (manufactured by Parus Co., Korea) for three days before and after inoculation. Light sources included purple (380 nm), blue (440 nm), white (470 nm), and red (660 nm) LEDs, as well as fluorescent lights (control). Evaluation of wildfire disease incidence. Leaves of 4- to 5-week-old plants treated with various wavelengths were infiltrated with Pseudomonas pv. tabaci (Pst), a bacterium pathogenic to N. benthamiana, grown at 28°C on King’s B medium (peptone 20 g, potassium sulphate 1.5 g, magnesium chloride 1.5 g, glycerol 10 ml, and agar 15 g). Bacterial cell suspensions (105 CFU/ml) were infiltrated in

Fig. 1. Symptoms on the leaves of N. benthamiana inoculated with P. syringae pv. tabaci.


mesophyll tissue of intact plants using a 1 ml hypodermic syringe without a needle. Leaves were harvested at the indicated time points (0, 1, 12, and 24 h) post inoculation, immediately frozen in liquid nitrogen, and stored at -80°C for future use. The diameter of lesions on pathogen-infected leaves was measured 5 days after infiltration. To monitor bacterial cell growth in infiltrated leaf tissues, discs (10 mm in diameter) of tissues incubated for 24 h were ground in 10 mM MgCl2, then spread on selective King’s B medium. The number of bacteria was determined based on the number of colonies formed on the media after 48 h incubation. RNA isolation, RT-PCR and real-time PCR. Total RNA was extracted using the easy-BLUE kit (iNtRON Biotechnology, USA) according to manufacturer’s instructions. First-strand cDNA was synthesized from 500 ng total RNA using a PrimeScript 1st strand cDNA synthesis kit (TaKaRa, Japan) and subsequently used as PCR template, using primer sequences of the housekeeping gene β-actin and the defense-related genes shown in Table 1. The conditions for PCR were as follows: initial denaturation at 94°C for 5 min, followed by 30 cycles at 94°C for 45 sec, 55°C for 45 sec, and 72°C for 1 min, and final extension for 7 min at 72°C. The various-sized PCR products were identified by 1% agarose gel electrophoresis. Quantitative real time PCR was carried out using the SYBR Premix Ex (TaKaRa Bio, Japan) with a final primer concentration of 500 nM and 2 ng of total cDNA in a Rotor-Gene 6000 (Qiagen, USA) using the following thermal cycling profile: 95°C for 15 min, followed by 40 cycles of 95°C for 20 sec, 60°C for 30 sec, and 72°C for 30 sec. Each real-time assay was tested for single PCR products using a high resolution melting profiling technique that identifies the amplicon as a single PCR product. The actin gene of Nicotiana tabacum (GenBank accession No. EU938079.1) was used as internal control gene for normalization and quantification of gene expression.

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Fig. 2. Disease development on the leaves of N. benthamiana inoculated with P. syringae pv. tabaci. The sizes of the lesions on inoculated N. benthamiana leaves (105 CFU/ml) were measured 5 days after bacterial infiltration. Mean separation within columns by Duncan’s multiple range test (p < 0.05).

Fig. 3. Number of colony forming units from N. benthamiana leaves inoculated with P. syringae pv. tabaci. (105 CFU/ml) and irradiated with LED light sources for 24 h. Mean separation within columns was determined by the Duncan’s multiple range test (p < 0.05).

RESULTS

LED irradiation than those exposed to fluorescent light irradiation. Induction of PR genes indicated that the inhibition of lesions in LED-irradiated N. benthamiana plants was related to the activation of defense responses. The high expression of several defense-related genes in inoculated plants grown under LEDs suggests that the exposure to light at various wavelengths provided by LEDs prevents disease development. Among the seven primer sets used for detection of the expression levels of defense-related genes in this study, those specific for the chalcone synthase (CHS), glutathione-S-transferase (GST), and thaumatin-like protein (TLP) genes were selected for further analysis by real-time PCR due to their high induction in response to the LED treatments (Fig. 5). Treatment with LEDs for three days enhanced the expression of these defense-related genes in N. benthamiana to a greater extent than treatment with fluorescent light. Similarly, the expression of these defenserelated genes was greater in plants inoculated with Pst after pre-treatment with LEDs for three days than in those that were not pre-treated with LEDs. Gene expression of GST increased gradually until 12 h post inoculation, then decreased. Among the treated LEDs, blue and red light resulted in a greater enhancement of GST and TLP gene expression (Fig. 5).

Inhibition of wildfire disease development by irradiation at various wavelengths. Development of wildfire disease lesions on the leaves of N. benthamiana plants was evaluated 5 days after Pst inoculation. N. benthamiana leaves showed bacterial wilt symptoms after infiltration (Fig. 1). Symptom development was inhibited in all plants irradiated with purple (380 nm), blue (440 nm), white (470 nm), and red light (660 nm) as compared to plants irradiated with fluorescent light 5 days post inoculation (Fig. 2). Among the various wavelengths, blue (440 nm) and red light (660 nm) induced the greatest inhibition effect on lesion development in N. benthamiana plants. The growth of bacteria in the control and the N. benthamiana leaves irradiated with LEDs was further measured by counting the colony forming units from leaves infiltrated with Pst for 24 h. The number of bacteria recovered from the lesions of leaves treated with LEDs was significantly lower than that recovered from fluorescent lighttreated plants (Fig. 3). Furthermore, bacterial cell growth in N. benthamiana leaves was effectively inhibited by irradiation with purple (380 nm) and red (660 nm) LEDs (Fig. 3). Expression profiles of defense-related genes in LEDirradiated N. benthamiana. As mentioned, RT-PCR was carried out using the primers listed in Table, using β-actin primers as internal control for RNA quality and quantity. RT-PCR analysis with eight primer sets for defense-related genes showed that those expressing pathogenesis-related protein Q (PR Q), proteinase inhibitor II (PinII), and thaumatin-like protein (TLP) were highly induced by inoculation with Pst and by LED irradiation for three days before inoculation with Pst (Fig. 4). Although the CAT gene was expressed in all treated plants, PinII, PR Q, and TLP were more highly expressed in plants subjected to


DISCUSSION

It has been reported that red lights induced resistance against B. cinerea-induced grey mould, the root-knot nematode Meloidogyne javanica and Pseudomonas syringae pv. tomato, as well as Corynespora leaf spot caused by Corynespora cassicola, and leaf spot caused by A. tenuissima in broad bean (Islam et al., 1998, 1999, 2002; Khanam et al., 2005; Rahman et al., 2003). Irradiation with red light

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Fig. 4. RT-PCR analysis for measurement of the expression levels of seven defense-related genes in N. benthamiana leaves treated with LEDs or fluorescent lights, and infiltrated with P. syringae pv. tabaci. Total RNAs were extracted at the indicated time points. Equal volume usage of total RNA was identified by comparing the expression levels of the actin gene. ACT, actin; ANS, anthocyanine synthase; CAT, catalase; CHS, chalcone synthase, GST, glutathione-S-transferase; PinII, protease inhibitor II, PR Q, pathogenesis-related protein Q; TLP, thaumatine-like protein.

was reported to inhibit the germination of spores and mycelial growth, which likely occurred via the accumulation of antimicrobial compounds to suppress the leaf spot disease incidence in cucumber (Rahman et al., 2010) and to induce resistance to M. grisea infection in rice (Arase et al., 2000, 2001). Kudo et al. (2009, 2011) reported that green light (450-560 nm) irradiation resulted in inhibition of strawberry anthracnose and cucumber grey mould by inducing expression of the AOS1 (allen oxide synthase 1) gene, which is related to disease resistance in plants. Light affects seed germination, growth, morphogenesis, and physiological activities of plants (Cho et al., 2008; Jeong et al., 2009). It also plays a pivotal role in plant defense against pathogens, and is required for the activation of several defense genes and regulation of cell death response (Fryer et al., 2003; Honda and Nemoto, 1985; Karpinski et al., 1999; Schuerger and Brown, 1997; Thomas et al., 1988; Vakalounakis and Christias, 1981). Plants respond to pathogen attacks by producing a wide range of PR proteins (Van Loon et al., 1994, 2006; Van Loon and Van Strien, 1999). The upregulation of PR Q, PinII and TLP induced by LED irradiation for three days before the inoculation of Pst observed in this study indicates that these genes play an important role in the inhibition of symptom development in N. benthamiana plants. Plant GSTs were induced in response to heavy metals, pathogen attacks, and oxidative stress to protect cellular components from damage (Levine et al., 1994; Marrs, 1996; Moons, 2003; Ulmasov et al., 1995). According to


Wagner et al. (2002), GST genes exhibit a diverse range of responses to pathogen infection, hormonal treatment of jasmonate, salicylic acid and ethylene, and oxidative stress in Arabidopsis. Enhancement of GST and TLP gene expression by LED irradiation is considered to have inhibited the growth of pathogenic bacteria and suppressed the incidence of lesions in plants as observed in this study. These findings are consistent with those of previous investigations in which red light irradiation was found to regulate the incidence of disease by induction of defense mechanisms in host plants (Islam et al., 1998, 1999; Rahman et al., 2003). Although our results provide useful information on the use of LEDs to reduce plant disease incidence as one of the means to exploit for integrated pest management in agricultural ecosystems, further studies are desirable for determining the optimal and most efficient LED irradiation system for a practical application to pest control in field-grown crops. ACKNOWLEDGEMENTS

This work was supported by the 2011 Post Doctoral Course Program of Yeungnam University, and the Technology Innovation Program (Industrial Strategic Technology Development Program, 10033630) funded by the Ministry of Knowledge Economy (MKE, Korea).

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Fig. 5. Quantitative real time PCR analysis of defense-related genes expression in N. benthamiana leaves infiltrated with P. syringae pv. tabaci. A, C, E, LED only; B, D, F, pretreated with LED for 3 days prior to inoculation. × fluorescent light; ○ purple; ● blue; □ white; ■ red light. REFERENCES Arase S., Fujita K., Uehara T., Honda Y., Isota J., 2000. Light enhanced resistance to Magnaporthe grisea infection in the rice Sekiguchi lesion mutant. Journal of Phytopathology 148: 197-203. Arase S., Ueno M., Toko M., Honda Y., Itoh K., Ozoe Y., 2001. Light-dependent accumulation of tryptamine in the rice Sekiguchi lesion mutant infected with Magnaporthe grisea. Journal of Phytopathology 149: 409-413. Barta D.J., Tibbitts T.W., Bula R.J., Morrow R.C., 1992. Evaluation of light-emitting diode characteristics for a spacebased plant irradiation source. Advances in Space Research 12: 141-149. Benedict W.G., 1997. Differential effect of light intensity on the infection of wheat by Septoria tritici Dsem under controlled environment conditions. Physiological and Molecular Plant Pathology 1: 55-66. Bula R.J., Morrow R.C., Tibbitts T.W., Barta D.J., Ignatius R.W., Martin T.S., 1991. Light-emitting diodes as a radiation


source for plants. Horticultural Science 26: 203-205. Cantos E., Espin J.C., Tomas-Barberan F.A., 2001. Postharvest induction modeling method using UV irradiation pulses for obtaining resveratrol-enriched table grapes: a new “functional” fruit? Journal of Agricultural and Food Chemistry 49: 5052-5058. Cantos E., Garcia-Viguera C., de Pascual-Teresa S., TomasBarberan F.A., 2000. Effect of postharvest ultraviolet irradiation on resveratrol and other phenolics of cv. Napoleon table grapes. Journal of Agricultural and Food Chemistry 48: 4606-4612. Chalutz E., Droby S., Wilson C.L., Wisniewski M.E., 1992. UV-induced resistance to post harvest disease of citrus fruit. Journal of Photochemistry and Photobiology 15: 367374. Cho J.Y., Son D.M., Kim J.M., Seo B.S., Yang S.Y., Kim B.W., Heo B.G., 2008. Effects of various LEDs on the seed germination, growth and physiological activities of rape (Brassica napus) sprout vegetable. Korean Journal of Plant Research 21: 304-309.

06/11/13 15:44

482


Creasy L., Coffee M., 1988. Phytoalexin production potential of grape berries. Journal of the American Society for Horticultural Science 113: 230-234. Date H., Kataoka E., Tanina K., Sasaki S., Inoue K., Nasu H., Kasuyama S., 2004. Sensitivity of Corynespora cassiicola, causal agent of Corynespora leaf spot of cucumber, to thiophanate-methyl, diethofencarb and azoxystrobin. Japanese Journal of Phytopathology 70: 10-13. Diaz B.M., Fereres A., 2007. Ultraviolet-blocking materials as a physical barrier to control insect pests and plant pathogens in protected crops. Pest Technology 1: 85-95. Droby E., Horve B., Cohen L., Gaba V., Wilson C.L., Wisniewski M.E., 1993. Factor affecting UV-induced resistance in grape fruit against the green mold decay caused by Penicillium digitatum. Plant Pathology 42: 418-424. Fritzemeier K., Kindl H., 1981. Coordinate induction by UV light of stilbene synthase phenylalanine ammonia-lyase and cinnamate 4-hydroxylase in leaves of Vitaceae. Planta 151: 48-52. Fryer M., Ball L., Oxborough K., Karpinski S., Mullineaux P., Baker N., 2003. Control of ascorbate peroxidase 2 expression by hydrogen peroxide and leaf water status during excess light stress reveals a functional organization of Arabidopsis leaves. Plant Journal 33: 691-705. Hamamoto H., Yamazaki K., 2009. Reproductive response of okra and native rosella to long-day treatment with red, blue, and green light-emitting diode lights. Horticultural Science 44: 1494-1497. Han E.J., Kozai T., Paek K.Y., 2000. Blue and red light emitting diodes with or without sucrose and ventilation affects in vitro growth of Rehmania glutinosa plantlets. Journal of Plant Biology 43: 247-250. Heo J.W., Lee C.W., Chakrabarty D., Paek K.Y., 2002. Growth responses of marigold and salvia bedding plants as affected by monochromic or mixture radiation provided by a lightemitting diode (LED). Plant Growth Regulation 38: 225-230. Hirama J., Seki K., Hosodani N., Matsui Y., 2007. Development of a physical control device for insect pests using a yellow LED light source: Results of behavioral observations of the Noctudae family. Journal of the Science of Food and Agriculture 19: 34-40. Hoenecke M.E., Bula R.J., Tibbitts T.W., 1992. Importance of blue photon levels for lettuce seedlings grown under redlight emitting diodes. Horticultural Science 27: 427-430. Honda Y., Nemoto M., 1985. Control of seedling blast of rice with ultraviolet-absorbing vinyl film. Plant Disease 69: 596598. Islam S.Z., Honda Y., Arase S., 1998. Light-induced resistance of broad bean against Botrytis cinerea. Journal of Phytopathology 146: 479-485. Islam S.Z., Honda Y., Arase S., 1999. Some characteristics of red light-induced substance(s) against Botrytis cinerea produced in broad bean leaflets. Journal of Phytopathology 147: 65-70. Islam S.Z., Honda Y., Sawa Y., Babadoost M., 2002. Characterization of antifungal glycoprotein in red-light-irradiated broad bean leaflets. Mycoscience 43: 471-473. Islam S.Z., Babadoost M., Bekal S., Lambert K., 2008. Red light-induced systemic disease resistance against root-knot


Journal of Plant Pathology (2013), 95 (3), 477-483 nematode Meloidogyne javanica and Pseudomonas syringae pv. tomato DC 3000. Journal of Phytopathology 156: 708-714. Jeong J.H., Kim Y.S., Moon H.K., Hwang S.J., Choi Y.E., 2009. Effects of LED on growth, morphogenesis and eleutheroside contents of in vitro cultured plantlets of Eleutherococcus senticosus Maxim. Korean Journal of Medicinal Crop Science 17: 39-45. Karpinski S., Reynolds H., Karpinska B., Wingsle G., Creissen G., Mullineaux P., 1999. Systemic signaling and acclimation in response to excess excitation energy in Arabidopsis. Science 284: 654-657. Khanam N.N., Kihara J., Honda Y., Tsukamoto T., Arase S., 2005. Studies on red light-induced resistance of broad bean to Botrytis cinerea: I. Possible production of suppressor and elicitor by germinating spores of pathogen. Journal of General Plant Pathology 71: 285-288. Kudo R., Ishida Y., Yamamoto K., 2011. Effect of green light irradiation on induction of disease resistance in plants. Acta Horticolturae 907: 251-254. Kudo R., Yamamoto K., Suekane A., Ishida Y., 2009. Development of green light pest control systems in plants. I. Studies on effects of green light irradiation on induction of disease resistance. SRI Research Reports 93: 31-35. Langcake P., Pryce R., 1976. The production of resveratrol by Vitis vinifera and other members of the Vitaceae as a response to infection or injury. Physiological and Molecular Plant Pathology 9: 77-86. Levine A., Tenhaken R., Dixon R., Lamb C., 1994. H2O2 from the oxidative burst orchestrates the plant hypersensitive disease resistance response. Cell 79: 583-593. Lian M.L., Murthy H.N., Paek K.Y., 2002. Effects of light emitting diodes (LEDs) on the in vitro induction and growth of bulblets of Lilium oriental hybrid ‘Pesaro’. HortScience 94: 365-370. Marrs K.A., 1996. The functions and regulation of glutathione S-transferases in plants. Annual Review of Plant Physiology and Plant Molecular Biology 47: 127-158. Moons A., 2003. Osgstu3 and osgtu4, encoding tau class glutathione S-transferases, are heavy metal- and hypoxic stressinduced and differentially salt stress-responsive in rice roots. FEMS Letters 53: 427-432. Rahman M.Z., Honda Y., Arase S., 2003. Red-light-induced resistance in broad bean (Vicia faba L.) to leaf spot disease caused by Alternaria tenuissima. Journal of Phytopathology 151: 86-91. Rahman M.Z., Khanam H., Ueno M., Kihara J., Honda Y., Arase S., 2010. Suppression by red light irradiation of Corynespora leaf spot of cucumber caused by Corynespora cassiicola. Journal of Phytopathology 158: 378-381. Rudolf J.R., Resurreccion A.V.A., 2005. Elicitation of resveratrol in peanut kernels by application of abiotic stresses. Journal of Agricultural and Food Chemistry 53: 10186-10192. Schuerger A.C., Brown C.S., 1997. Spectral quality affects disease development of three pathogens on hydroponically grown plants. HortScience 32: 96-100. Subba Rao P.V., Wadia K.D.R., Strange R.N., 1996. Biotic and abiotic elicitation of phytoalexins in leaves of groundnut (Arachis hypogaea L.). Physiological and Molecular Plant Pathology 49: 343-357.

06/11/13 15:44

Journal of Plant Pathology (2013), 95 (3), 477-483 Tabira H., Otani H., Shimomura N., Kodama M., Kohmoto K., Nishimura S., 1989. Light-induced insensitivity of apple and Japanese pear leaves to AM-toxin from Alternaria alternata apple-pathotype. Annals of the Phytopathological Society of Japan 55: 567-578. Thomas P.E., Hassan S., Mink G.I., 1988. Influence of light quality on translocation of Tomato yellow top virus and Potato leaf roll virus in Lycopersicon peruvianum and some of its tomato hybrids. Phytopathology 78: 1160-1164. Ulmasov T., Ohmiya A., Hagen G., Guilfoyle T., 1995. The soybean GH2/4 gene that encodes a glutathione-S-transferase has a promoter that is activated by a wide range of chemical agents. Plant Physiology 108: 919-927. Vakalounakis D.J., Christias C., 1981. Sporulation in Alternaria cichorii is controlled by a blue and near ultraviolet reversible

Ahn et al. 483 photoreaction. Canadian Journal of Botany 59: 626-628. Van Loon L.C., Pierpoint W.S., Boller T., Conejero V., 1994. Recommendations for naming plant pathogenesis-related proteins. Plant Molecular Biology Reporter 12: 245-264. Van Loon L.C., Van Strien E.A., 1999. The family of pathogenesis related proteins, their activities, and comparative analysis of PR-1 type proteins. Physiological and Molecular Plant Pathology 55: 85-97. Van Loon L.C., Rep M., Pieterse C.M.J., 2006. Significance of inducible defense-related proteins in infected plants. Annual Review of Phytopathology 44: 135-162. Wagner U., Edwards R., Dixon D.P., Mauch F., 2002. Probing the diversity of the Arabidopsis glutathione-S-transferase gene family. Plant Molecular Biology 49: 515-532.

Received August 13, 2012 Accepted January 3, 2013


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