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Abstract <p><i>Flammulina filiformis</i> is a commercially important edible mushroom whose sexual compatibility is determined by genes at two unlinked mating-type loci, <i>A</i> and <i>B</i>. However, the molecular basis of <i>MAT-A</i> activation in this species remains unclear. Here, we established a pair of compatible monokaryotic strains, F11 and F22, derived from the dikaryotic parent ACCC50407, and used them to investigate the genomic and functional basis of <i>MAT-A</i> activation. Genome analysis showed that the <i>MAT-A</i> locus is bipartite, comprising the <i>Aa</i> and <i>Ab</i> subloci. Five <i>HD</i> genes were identified, including one <i>Aa</i>-encoded gene (<i>aHD2-1</i>) and four <i>Ab</i>-encoded genes. In yeast assays, aHD2-1 showed no detectable partner interaction or transcriptional activation activity, whereas specific interactions were detected between the <i>Ab</i>-encoded bHD1 and bHD2 proteins. Deletion analysis further indicated that bHD1-1 contains a functional C-terminal transcriptional activation domain whose activity is constrained in the full-length protein. In vivo, introduction of the compatible allele <i>bHD1-2</i> into F11 induced pseudoclamp formation and increased <i>clp1</i> expression. Guided by these results, we constructed a chimeric <i>HD</i> gene, <i>F11ChiHD</i>, by combining the N-terminal region of bHD2-1 with the C-terminal activation region of bHD1-1, which similarly promoted pseudoclamp formation and <i>clp1</i> upregulation in F11. Together, these findings indicate that <i>MAT-A</i> activation in <i>F. filiformis</i> depends primarily on the <i>Ab</i> sublocus and provide a genetic and functional framework for understanding mating-pathway regulation in this species.</p> Key points <p>• <i>MAT-A pathway activation in Flammulina filiformis is driven primarily by the Ab sublocus.</i></p> <p>• <i> Relief of bHD1 autoinhibition is associated with pseudoclamp formation and clp1 upregulation in monokaryotic F11.</i></p> <p>•<i>&#xa0;A chimeric HD protein supports modular coupling between HD2-associated DNA targeting and bHD1-associated transcriptional activation.</i></p>

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Relief of bHD1 autoinhibition and modular coupling support MAT-A pathway activation in Flammulina filiformis

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月15日

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  • Jinwei Zhang,
  • Yu Tian,
  • Xuyang Xiang,
  • Qinghao Fan,
  • Ruiying Zhang

摘要

Abstract

Flammulina filiformis is a commercially important edible mushroom whose sexual compatibility is determined by genes at two unlinked mating-type loci, A and B. However, the molecular basis of MAT-A activation in this species remains unclear. Here, we established a pair of compatible monokaryotic strains, F11 and F22, derived from the dikaryotic parent ACCC50407, and used them to investigate the genomic and functional basis of MAT-A activation. Genome analysis showed that the MAT-A locus is bipartite, comprising the Aa and Ab subloci. Five HD genes were identified, including one Aa-encoded gene (aHD2-1) and four Ab-encoded genes. In yeast assays, aHD2-1 showed no detectable partner interaction or transcriptional activation activity, whereas specific interactions were detected between the Ab-encoded bHD1 and bHD2 proteins. Deletion analysis further indicated that bHD1-1 contains a functional C-terminal transcriptional activation domain whose activity is constrained in the full-length protein. In vivo, introduction of the compatible allele bHD1-2 into F11 induced pseudoclamp formation and increased clp1 expression. Guided by these results, we constructed a chimeric HD gene, F11ChiHD, by combining the N-terminal region of bHD2-1 with the C-terminal activation region of bHD1-1, which similarly promoted pseudoclamp formation and clp1 upregulation in F11. Together, these findings indicate that MAT-A activation in F. filiformis depends primarily on the Ab sublocus and provide a genetic and functional framework for understanding mating-pathway regulation in this species.

Key points

• MAT-A pathway activation in Flammulina filiformis is driven primarily by the Ab sublocus.

• Relief of bHD1 autoinhibition is associated with pseudoclamp formation and clp1 upregulation in monokaryotic F11.

• A chimeric HD protein supports modular coupling between HD2-associated DNA targeting and bHD1-associated transcriptional activation.