TeA is a key virulence factor for Alternaria alternata (Fr.) Keissler infection of its host.
A toxin-deficient mutant strain, HP001 mutant of Alternaria alternata, whose mycelium is unable to infect its host, produces little tenuazonic acid (TeA) toxin. How TeA plays a role in initiating host infection by A. alternata remains unclear. In this research we use Imaging-PAM based on chlorophyll fluorescence parameters and transmission electron microscopy to explore the role of TeA toxin during the infection process of A. alternata. Photosystem II damage began even before wild type mycelium infected the leaves of its host, croftonweed (Ageratina adenophora). Compared with the wild type, HP001 mutant produces morphologically different colonies, hyphae with thinner cell walls, has higher reactive oxygen species (ROS) content and lower peroxidase activity, and fails to form appressoria on the host surface. Adding TeA toxin allows the mutant to partially recover these characters and more closely resemble the wild type. Additionally, we found that the mutant is able to elicit disease symptoms when its mycelium is placed on leaves whose epidermis has been manually removed, which indicates that TeA may be determinant in the fungus recognition of its plant host. Lack of TeA toxin appears responsible for the loss of pathogenicity of the HP001 mutant. As a key virulence factor, TeA toxin not only damages the host plant but also is involved in maintaining ROS content, host recognition, inducing appressoria to infect the host and for allowing completion of the infection process.
Weed Research Laboratory of Nanjing Agricultural University, No.1 Weigang, Xuanwu District, Nanjing 210095, China.
Ye
Y
Kang
Weed Research Laboratory of Nanjing Agricultural University, No.1 Weigang, Xuanwu District, Nanjing 210095, China.
Hongwei
H
Feng
Weed Research Laboratory of Nanjing Agricultural University, No.1 Weigang, Xuanwu District, Nanjing 210095, China.
Jingxu
J
Zhang
Weed Research Laboratory of Nanjing Agricultural University, No.1 Weigang, Xuanwu District, Nanjing 210095, China.
Shiguo
S
Chen
Weed Research Laboratory of Nanjing Agricultural University, No.1 Weigang, Xuanwu District, Nanjing 210095, China; Investigación y Desarrollo en Agricultura Tropical, P.O.Box 2191, Alajuela 4050, Costa Rica.
Bernal E
BE
Valverde
Weed Research Laboratory of Nanjing Agricultural University, No.1 Weigang, Xuanwu District, Nanjing 210095, China. Electronic address: wrl@njau.edu.cn.
Sheng
S
Qiang
D036603:Ageratina / Q000378:metabolism*; D000528:Alternaria / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D010935:Plant Diseases; D018515:Plant Leaves / Q000382:microbiology; D013720:Tenuazonic Acid / Q000378:metabolism / Q000633:toxicity*; D037521:Virulence Factors / Q000378:metabolism / Q000633:toxicity*
D005656:Fungal Proteins; D037521:Virulence Factors; D013720:Tenuazonic Acid
Alternaria alternata; Reactive oxygen species (ROS); Tenuazonic acid (TeA); Virulence factor