Cloning, Heterologous Expression, and Antifungal Activity Evaluation of a Novel Truncated TasA Protein from Bacillus amyloliquefaciens BS-3

<i>TasA</i> gene, encoding a functional amyloid protein critical for biofilm formation and antimicrobial activity, was cloned from the endophytic strain <i>Bacillus amyloliquefaciens</i> BS-3, isolated from rubber tree roots. This study identified the shortest functional <i>TasA</i> variant (483 bp, 160 aa) reported to date, featuring unique amino acid substitutions in conserved domains. Bioinformatics analysis predicted a signal peptide (1-27 aa) and transmembrane domain (7-29 aa), which were truncated to optimize heterologous expression. Two prokaryotic vectors (<i>pET28a</i> and <i>pCZN1</i>) were constructed, with <i>pCZN1</i>-<i>TasA</i> expressed solubly in <i>Escherichia coli</i> Arctic Express at 15 °C, while <i>pET28a</i>-<i>TasA</i> formed inclusion bodies at 37 °C. Purified recombinant TasA exhibited potent antifungal activity, achieving 98.6% ± 1.09 inhibition against <i>Colletotrichum acutatum</i>, 64.77% ± 1.34 against <i>Alternaria heveae</i>. Notably, TasA completely suppressed spore germination in <i>C. acutatum</i> and <i>Oidium heveae</i> Steinmannat 60 μg/mL. Structural analysis via AlphaFold3 revealed that truncation enhanced protein stability. These findings highlight BS-3-derived TasA as a promising biocontrol agent, providing molecular insights for developing protein-based biopesticides against rubber tree pathogens.