关键词: 玉米大斑病菌, StSCD家族, 黑色素, 环丙酰菌胺

Abstract: 【Objective】Scytalone dehydratase (SCD) is a key enzyme in melanin synthesis. The purpose of this paper is to identify the StSCD gene family of Setosphaeria turcica, and to analyze the differences in the expression of StSCD gene family during the appressorium development of S. turcica and the effect of SCD inhibitors on melanin synthesis, laying a foundation for further research on the important role of the StSCD gene family in melanin synthesis and appressorium development. 【Method】Using the whole genome data of the wild-type strain 01-23 of S. turcica, the complete sequence of the StSCD gene family was obtained, and the sequences were compared with the SCD genes of Cochlibolus heterostrophus, Pyricularia oryzae, Colletotrichum lagenaria and other fungi. Collected materials from different appressorium  developmental stages for RT-PCR analysis to obtain the expression levels of different StSCDs genes at different stages, so as to determine the important dehydratase genes closely related to pathogen infection and appressorium melanization. Carpropamid, an inhibitor of SCD, was used to treat S. turcica, and the colony growth rate, melanin production and appressorium turgor pressure were measured, so as to determine the important function of SCD in appressorium development. 【Result】Four StSCD genes were found by searching the whole genome of S. turcica, the encoded protein of them has SCD conserved domain and conserved catalytic and substrate binding amino acid residues.  StSCD3 protein had high homology with the functionally redundant SCD2 protein of Botrytis cinerea, and StSCD4 has high homology with SCD proteins involved in melanin synthesis in pathogenic fungi. By analyzing the expression levels of StSCD genes at different stages during the growth and development of the pathogen, it was found that the expression levels of four StSCD genes were all up-regulated in the appressorium stage, and the expression levels of StSCD3 and StSCD4 were particularly up-regulated. The expression levels of StSCDs 6 h after appressorium formation were significantly decreased, and the expression levels of StSCD3 and StSCD4 were higher during the whole period of appressorium induction. The melanin synthesis was blocked and the appressorium pressure was significantly reduced after carpropamid treatment. 【Conclusion】There are four StSCD genes in S. turcica. It is speculated that StSCD4 is involved in the synthesis of DHN melanin, and then affects the accumulation of appressorium. The above research results lay a foundation for further elucidating the gene function of StSCDs of S. turcica.

Key words: Setosphaeria turcica, StSCD , family, melanin, carpropamid