AtNFXL1, an Arabidopsis homologue of the human transcription factor NF-X1, functions as a negative regulator of the trichothecene phytotoxininduced defense response. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Journal: The Plant JournalTrichothecenes are a closely related family of phytotoxins produced by phytopathogenic fungi. In Arabidopsis, expression of AtNFXL1, a homologue of the putative human transcription repressor NF-X1, was significantly induced by application of type A trichothecenes, such as T-2 toxin. An atnfxl1 mutant growing on medium lacking trichothecenes showed no phenotype, whereas a hypersensitivity phenotype was observed in T-2 toxin-treated atnfxl1 mutant plants. Microarray analysis indicated that several defense-related genes (i.e. WRKYs, EDS5, ICS1, etc.) were upregulated in T-2 toxin-treated atnfxl1 mutant compared to wild type plants. In addition, enhanced salicylic acid (SA) accumulation was observed in T-2 toxin-treated atnfxl1 mutant plants, which suggests that AtNFXL1 functions as a negative regulator of these defense-related genes via an SA-dependent signaling pathway. We also found that expression of AtNFXL1 was induced by SA and flg22 treatment. Moreover, the atnfxl1 mutant was less susceptible to a compatible phytopathogen, Pseudomonas syringae pv. tomato strain DC3000 (Pst DC3000). Taken together, these results indicate 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60Trichothecenes are a major type of mycotoxin, and are important in human health due to the risk of ingesting contaminated food (Kimura et al., 2006). Phytopathogenic fungi capable of producing trichothecenes are found throughout the world, and include certain species of Fusarium, Myrotherium and Stachybotrys (Eudes et al., 2001). The production of mycotoxins by these species of phytopathogenic fungi is determined by genetic factors and environmental growth conditions. Trichothecenes have a sesquiterpenoid ring structure, and can be classified according to the presence or absence of characteristic functional groups (Shifrin and Anderson, 1999). Type A trichothecenes, such as T-2 toxin, and type B trichothecenes, such as deoxynivalenol (DON), are natural contaminants of certain agricultural commodities, as well ...