title: Involvement of a helix-loop-helix transcription factor CHC-1 in CO(2)-mediated conidiation suppression in Neurospora crassa.
abstract: The morphological switch from vegetative growth to conidiation in filamentous fungi is highly regulated, but the understanding of the regulatory mechanisms is limited. In this study, by screening a set of knock-out mutants corresponding to 103 transcription factor encoding genes in Neurospora crassa, a mutant was found to produce abundant conidia in race tubes in which conidiation in the wild-type strain was suppressed. The corresponding gene NCU00749 encodes a protein containing a helix-loop-helix DNA binding region. Unlike enhanced conidiation in ras-1 and sod-1 mutants, which was completely suppressed by antioxidant N-acetyl cysteine, enhanced conidiation in the NCU00749 mutant was only slightly affected by N-acetyl cysteine. When grown on slants, the NCU00749 deletion mutant exhibited earlier conidial formation than the wild-type strain, and this was more evident at a higher (5%) CO(2) concentration. Therefore, we named NCU00749 as conidiation at high carbon dioxide-1 (chc-1). Genes that are highly expressed during conidial development, eas, con-6, con-8 and con-10, were transcribed at a higher rate in the chc-1 deletion mutant than the wild-type strain in response to conidiation induction. To determine the mechanisms by which CHC-1 regulates conidiation, we conducted a RNA sequencing analysis and found that 404 genes exhibited ≥ 2 fold changes in transcription in response to chc-1 deletion. Among them, fluffy and ada-6, two transcription factor genes that positively regulate conidiation in N. crassa, and rca-1, whose homolog flbD in Aspergillus nidulans is essential for conidiation, were upregulated in the chc-1 deletion mutant. Results of RNA sequencing also suggest that signal transduction via the cAMP and the MAK-2 mediated signal pathways, and ROS generation and removal, mechanisms known to regulate conidiation, are not involved in chc-1 mediated control of conidiation. In addition, chc-1 also influences expression of genes involved in other important biological processes besides conidiation such as carbon metabolism, sphingolipid synthesis, cell wall synthesis, and calcium signaling.
authors: Key Laboratory of Systematic Mycology and Lichenology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, China.
authors: Xianyun
authors: X
authors: Sun
authors: Hanxing
authors: H
authors: Zhang
authors: Zhenying
authors: Z
authors: Zhang
authors: Yong
authors: Y
authors: Wang
authors: Shaojie
authors: S
authors: Li
mesh_terms: D001483:Base Sequence; D002245:Carbon Dioxide / Q000494:pharmacology; D004271:DNA, Fungal / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D018257:Helix-Loop-Helix Motifs / Q000235:genetics; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D017423:Sequence Analysis, RNA; D015398:Signal Transduction; D013172:Spores, Fungal / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; D014157:Transcription Factors; D002245:Carbon Dioxide