High mobility group protein (HMG), as a widespread eukaryotic protein, plays an important role in the regulation of fungal growth and development. This study aims to identify the HMG family members of Botrytis cinerea through the genome-wide identification, and analyze their expression rules during the growth and development, infection and response to stress, so as to lay a foundation for further investigation of the function of this family gene in the growth and development and pathogenic mechanism of B. cinerea.

HMMER software was used to screen out possible HMG gene IDs in B. cinerea protein database, and the online tools Pfam and SMART were used to verify the possible HMG family members. Using ProtParam, TBtools, MEME, MEGA, MCScanX and other tools, the physicochemical characteristics, chromosome localization, gene structure, phylogenetic tree and collinearity of B. cinerea HMG gene family members were analyzed. Based on transcriptome sequencing data of B. cinerea during conidial development and infection, the expression of HMG family genes in B. cinerea during conidial development and infection was analyzed by using TBtools software. In addition, the expression of HMG family genes in B. cinerea under NaCl, KCl, H₂O₂ and other stresses was observed by real-time quantitative PCR (qPCR).

Nine HMG family members were identified in B. cinerea, the number of encoded amino acids ranged from 101 to 1076, and the molecular weight ranged from 11.48 to 120.64 kDa. They could be divided into HMGA and HMGB subfamilies, which had conserved HMG domain, distributed on six chromosomes, and had gene collinearity with Fusarium graminearum and Fusarium oxysporum. The expression pattern analysis showed that the expression levels of this family gene showed obvious changes during conidial development and B. cinerea infection. Among them, Bcin01g08840, Bcin07g04610, Bcin11g04340 and Bcin11g03320 continued to be highly expressed during conidial development. The expression levels of Bcin07g04610, Bcin11g04340, Bcin11g05790 and Bcin01g08840 were significantly down-regulated during B. cinerea infection. qPCR analysis showed that the gene expression of this family was significantly down-regulated after NaCl and KCl stress treatment.

B. cinerea contains nine HMG family members, which can be divided into HMGA and HMGB subfamilies, the members distribute on six chromosomes, and have different expression patterns in the process of conidial development, infection and stress response of the pathogen. It is speculated that the family genes play an important role in the growth and development, pathogenicity and stress response of B. cinerea.