title: Induction of DIMBOA accumulation and systemic defense responses as a mechanism of enhanced resistance of mycorrhizal corn (Zea mays L.) to sheath blight.
abstract: Arbuscular mycorrhizas are the most important symbioses in terrestrial ecosystems and they enhance the plant defense against numerous soil-borne pathogenic fungi and nematodes. Two corn (Zea mays) varieties, Gaoyou-115 that is susceptible to sheath blight disease caused by Rhizoctonia solani and Yuenong-9 that is resistant, were used for mycorrhizal inoculation in this study. Pre-inoculation of susceptible Gaoyou-115 with arbuscular mycorrhizal fungus (AMF) Glomus mosseae significantly reduced the disease incidence and disease severity of sheath blight of corn. HPLC analysis showed that AMF inoculation led to significant increase in 2,4-dihydroxy-7-methoxy-2 H-1,4-benzoxazin-3(4 H)-one (DIMBOA) accumulation in the roots of both corn varieties and in leaves of resistant Yuenong-9. R. solani inoculation alone did not result in accumulation of DIMBOA in both roots and leaves of the two corn varieties. Our previous study showed that DIMBOA strongly inhibited mycelial growth of R. solani in vitro. Real-time PCR analysis showed that mycorrhizal inoculation itself did not affect the transcripts of most genes tested. However, pre-inoculation with G. mosseae induced strong responses of three defense-related genes PR2a, PAL, and AOS, as well as BX9, one of the key genes in DIMBOA biosynthesis pathway, in the leaves of corn plants of both Yuenong-9 and Gaoyou-115 after the pathogen attack. Induction of defense responses in pre-inoculated plants was much higher and quicker than that in non-inoculated plants upon R. solani infection. These results indicate that induction of accumulation of DIMBOA, an important phytoalexin in corn, and systemic defense responses by AMF, plays a vital role in enhanced disease resistance of mycorrhizal plants of corn against sheath blight. This study also suggests that priming is an important mechanism in mycorrhiza-induced resistance.
authors.affiliation: Key Laboratory of Ecological Agriculture, Ministry of Agriculture, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Key Laboratory of Agroecology and Rural Environment of Guangdong Regular Higher Education Institutions, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Institute of Tropical and Subtropical Ecology, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.
authors.forename: Yuan Yuan
authors.initials: YY
authors.lastname: Song
authors.affiliation: Key Laboratory of Ecological Agriculture, Ministry of Agriculture, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Key Laboratory of Agroecology and Rural Environment of Guangdong Regular Higher Education Institutions, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Institute of Tropical and Subtropical Ecology, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.
authors.forename: Man
authors.initials: M
authors.lastname: Cao
authors.affiliation: Key Laboratory of Ecological Agriculture, Ministry of Agriculture, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Key Laboratory of Agroecology and Rural Environment of Guangdong Regular Higher Education Institutions, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Institute of Tropical and Subtropical Ecology, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.
authors.forename: Li Jun
authors.initials: LJ
authors.lastname: Xie
authors.affiliation: Key Laboratory of Ecological Agriculture, Ministry of Agriculture, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Key Laboratory of Agroecology and Rural Environment of Guangdong Regular Higher Education Institutions, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Institute of Tropical and Subtropical Ecology, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.
authors.forename: Xiao Ting
authors.initials: XT
authors.lastname: Liang
authors.affiliation: Key Laboratory of Ecological Agriculture, Ministry of Agriculture, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China. rszeng@scau.edu.cn.|Key Laboratory of Agroecology and Rural Environment of Guangdong Regular Higher Education Institutions, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China. rszeng@scau.edu.cn.|Institute of Tropical and Subtropical Ecology, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China. rszeng@scau.edu.cn.
authors.forename: Ren Sen
authors.initials: RS
authors.lastname: Zeng
authors.affiliation: Key Laboratory of Ecological Agriculture, Ministry of Agriculture, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Key Laboratory of Agroecology and Rural Environment of Guangdong Regular Higher Education Institutions, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Institute of Tropical and Subtropical Ecology, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.
authors.forename: Yi Juan
authors.initials: YJ
authors.lastname: Su
authors.affiliation: Institute of Tropical and Subtropical Ecology, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.
authors.forename: Jing Hua
authors.initials: JH
authors.lastname: Huang
authors.affiliation: Key Laboratory of Ecological Agriculture, Ministry of Agriculture, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Key Laboratory of Agroecology and Rural Environment of Guangdong Regular Higher Education Institutions, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Institute of Tropical and Subtropical Ecology, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.
authors.forename: Rui Long
authors.initials: RL
authors.lastname: Wang
authors.affiliation: Key Laboratory of Ecological Agriculture, Ministry of Agriculture, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Key Laboratory of Agroecology and Rural Environment of Guangdong Regular Higher Education Institutions, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.|Institute of Tropical and Subtropical Ecology, South China Agricultural University, Wushan, Guangzhou, 510642, People's Republic of China.
authors.forename: Shi Ming
authors.initials: SM
authors.lastname: Luo
mesh_terms: D048588:Benzoxazines / Q000276:immunology*; D060467:Disease Resistance; D018506:Gene Expression Regulation, Plant; D055137:Glomeromycota / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D038821:Mycorrhizae / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D012232:Rhizoctonia / Q000502:physiology; D003313:Zea mays / Q000235:genetics / Q000276:immunology* / Q000382:microbiology
chemical_list: D048588:Benzoxazines; C050733:2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one