关键词: 玉米大斑病菌, Septin基因家族, 实时荧光定量PCR, 基因表达

Abstract:

【Background】Septin, which is widely found in all eukaryotes except plants, is a highly conserved GTP binding protein family and is considered to be the fourth cytoskeletal protein after microtubules, microfilaments and intermediate fibers. Septin proteins of pathogenic fungi are involved in cell polarity determination, morphological shaping and morphological transformation associated with pathogenicity.【Objective】The objective of this study is to identify Septin gene family of Setosphaeria turcica, analyze its expression pattern at different developmental stages, and to lay a foundation for clarifying the relationship between the membrane protein Septin and fungal infection structure development.【Method】The amino acid sequences of six Septin proteins in Bipolaris maydis were used as probe sequences, online Blastp alignment and keyword search were carried out in the S. turcica database to obtain S. turcica candidate Septins. Then bioinformatics analyses including gene structure, physical and chemical properties and transmembrane region structure of the Septins were conducted. The materials of S. turcica that were induced by artificial hydrophobic media at different stages of infective structures development and infected host leaves at different times were collected, and RT-qPCR (real-time fluorescence quantitative PCR) technology was used to analyze the transcription levels of Septins at different stages of infective structures development.【Result】Six candidate Septins were obtained, and among them, four typical Septins contained G1, G3, and G4 motifs, were named by StSep1, StSep2, StSep3 and StSep4, respectively. The expression level of Septins increased slowly under the induction on artificial hydrophobic media. StSep1 was active in the late stage of germ tube formation, and its expression level was 25.69 times of that in the conidia period (P<0.01). The expression level of StSep4 reached a peak in appressorium anaphase, and then the expression level was down-regulated. The change trend of Septin expression in the process of pathogen infection was basically consistent with that under the induction of artificial hydrophobic material. StSep1 expression was significantly up-regulated at 6 h after inoculation (P<0.01). As time went on, StSep4 actively expressed during the period of appressorial formation, and the expression reached a peak at 18 h after inoculation. After that, the expression was down-regulated, but it was still higher than that in the early stage of germination. StSep2 and StSep3 were active at 18 h and 24 h after inoculation, exceeding the initial stage of germination.【Conclusion】There are 4 core Septins in the genome of S. turcica. StSep1 and StSep4 are actively expressed during the formation of germ tube and appressoria, respectively. The results will provide a theoretical basis for further clarifying the function of Septin and the infection regulation mechanism of S. turcica.

Key words: Setosphaeria turcica, Septin gene family, RT-qRCR, gene expression