The Homeobox BcHOX8 Gene in Botrytis Cinerea Regulates Vegetative Growth and Morphology

Abstract

Filamentous growth and the capacity at producing conidia are two critical aspects of most fungal life cycles, including that of many plant or animal pathogens. Here, we report on the identification of a homeobox transcription factor encoding gene that plays a role in these two particular aspects of the development of the phytopathogenic fungus Botrytis cinerea. Deletion of the BcHOX8 gene in both the B. cinerea B05-10 and T4 strains causes similar phenotypes, among which a curved, arabesque-like, hyphal growth on hydrophobic surfaces; the mutants were hence named Arabesque. Expression of the BcHOX8 gene is higher in conidia and infection cushions than in developing appressorium or mycelium. In the Arabesque mutants, colony growth rate is reduced and abnormal infection cushions are produced. Asexual reproduction is also affected with abnormal conidiophore being formed, strongly reduced conidia production and dramatic changes in conidial morphology. Finally, the mutation affects the fungus ability to efficiently colonize different host plants. Analysis of the B. cinerea genome shows that BcHOX8 is one member of a nine putative homeobox genes family. Available gene expression data suggest that these genes are functional and sequence comparisons indicate that two of them would be specific to B. cinerea and its close relative Sclerotinia sclerotiorum.

Light governs asexual differentiation in the grey mould fungus Botrytis cinerea via the putative transcription factor BcLTF2

“…Bcpks13 encodes the key enzyme for conidial melanogenesis (Schumacher, ), bcltf12 encodes a Myb‐TF (orthologue of A. nidulans FlbD and N. crassa RCA‐1), bcltf15 encodes a C2H2‐TF (orthologue of A. nidulans FlbC), and bcltf16 encodes a transcriptional regulator (orthologue of A. nidulans MedA and N. crassa ACON‐3). BcfluG is the orthologue of A. nidulans fluG having no obvious function (Schumacher et al ., ), and bchox8 encodes a homeobox‐TF involved in morphogenesis and virulence (Antal et al ., ). B .…”

“…Further TFs affecting conidiation are the homeobox‐TF BcHOX8, the bZIP‐TF BcATF1 and the putative transcriptional regulator BcREG1. Deletion of bchox8 results in malformed conidia and conidiophores (Antal et al ., ), deletion of bcatf1 in excessive aerial hyphae formation accompanied by decreased numbers of conidia (Temme et al ., ), and the deletion of bcreg1 prevents the differentiation of conidia at regularly developed conidiophores (Michielse et al ., ).…”

Changes in the Sclerotinia sclerotiorum transcriptome during infection of Brassica napus

“…In the current study, a gene (SS1G_03835) encoding a homeobox C2H2 TF was expressed at 48 hpi, but the precise function of this gene in S. sclerotiorum needs to be characterized. A homeobox TF (BcHOX8) that plays a role in the vegetative growth and conidiogenesis has been reported in B. cinerea [148]. …”

The formation of sesquiterpenoid presilphiperfolane and cameroonane metabolites in the Bcbot4 null mutant of Botrytis cinerea

“…For each gene, a KnockOut (KO) cassette consisting of the 5′ region of bcbot, the nat resistance gene and the 3′ region bcbot was generated by double-joint PCR fusion 24 as previously described for B. cinerea. 25 All the PCR primers have been reported. 19 Protoplasts from the B05.10 strain were prepared and transformed as previously described.…”