Chitinase AbChi1 acts with the carbohydrate-binding module AbCbm1 to regulate mycelial growth in Agaricus bisporus

Exploring the role and mechanism of chitinase in the Agaricus bisporus is of great significance in regulating mycelial growth and development of A. bisporus. Based on this, the study first cloned the AGABI2DRAFT_211936 gene (screened by pre-transcriptomics) in the A₁₅ strain and designated as AbChi1. The carbohydrate-binding module gene AGABI2DRAFT_193505 (AbCbm1) was identified as a potential interacting partner of AbChi1 through yeast two-hybrid screening. The functions of AbCbm1 and AbChi1 were elucidated through gene silencing and overexpression techniques. Experimental results showed that the growth rate of the AbChi1 overexpression strain (AbChi1-ov) was 21.7 % slower than the wild-type strain, with its chitin content reduced by 17.44 % and 10.44 % compared to the AbChi1-RNAi strain and the wild-type strain, respectively. Similarly, the growth rate of the AbCbm1 overexpression strain (AbCbm1-ov) was 53.7 % slower than the wild-type strain, and its chitin content was 17.96 % and 8.63 % lower than that of the AbCbm1-RNAi and wild-type strains, respectively. Scanning electron microscopy revealed significantly reduced mycelial density and cross-sectional area in the overexpression strains for both genes were compared to their silenced and wild-type counterparts, confirming that overexpression of AbChi1 and AbCbm1 effectively delayed mycelial growth in A. bisporus. Protein interaction analyses using yeast two-hybrid and GST-pull down assays confirmed a direct interaction between AbChi1 and AbCbm1. The research findings provide theoretical foundations and important references for elucidating the growth regulation mechanisms in A. bisporus.