Open AccessRecognition of a core fragment of B eauveria bassiana hydrophobin gene promoter ( P hyd1 ) and its special use in improving fungal biocontrol potential
Author(s) -
Wang ZhengLiang,
Ying ShengHua,
Feng MingGuang
Publication year - 2013
Publication title -
microbial biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.287
H-Index - 74
ISSN - 1751-7915
DOI - 10.1111/j.1751-7915.2012.00351.x
Subject(s) - biology , beauveria bassiana , microbiology and biotechnology , hydrophobin , bassiana , conidium , gene , gene expression , heterologous expression , bacillus thuringiensis , biological pest control , bacteria , botany , genetics , recombinant dna
Summary To identify a suitable promoter for use in engineering fungal entomopathogens to improve heterologous gene expression and fungal biocontrol potential, a 1798 bp promoter ( P hyd1 ) upstream of B eauveria bassiana class I hydrophobin gene ( hyd1 ) was optimized by upstream truncation and site‐directed mutation. A truncated 1290 bp fragment ( P hyd1‐t1 ) drove eGFP expression in B . bassiana much more efficiently than full‐length P hyd1 . Further truncating P hyd1‐t1 to 1179, 991 and 791 bp or mutating one of the binding domains of three transcription factors in P hyd1‐t1 reduced significantly the expression of eGFP (enhanced green fluorescence protein). Under P hyd1‐t1 control, eGFP was expressed more abundantly in conidiogenic cells and conidia than in mycelia. Therefore, P hyd1‐t1 was used to integrate a bacterium‐derived, insect midgut‐specific toxin ( vip3Aa1 ) gene into B . bassiana , yielding a transgenic strain ( BbHV 8) expressing 9.8‐fold more toxin molecules in conidia than a counterpart strain ( BbV 28) expressing the toxin under the control of P gpdA , a promoter widely used for gene expression in fungi. Consequently, BbHV 8 showed much higher per os virulence to S podoptera litura larvae than BbV 28 in standardized bioassays with normal conidia for both cuticle penetration and ingestion or heat‐killed conidia for ingestion only. Conclusively, P hyd1‐t1 is a useful tool for enhancing beneficial protein expression, such as vip3Aa1 , in fungal conidia, which are the active ingredients of mycoinsecticides.