Genetic basis for coordination of meiosis and sexual structure maturation in Cryptococcus neoformans

Abstract

In the human fungal pathogen Cryptococcus neoformans, sex can benefit its pathogenicity through production of meiospores, which are believed to offer both physical and meiosis-created lineage advantages for its infections. Cryptococcus sporulation occurs following two parallel events, meiosis and differentiation of the basidium, the characteristic sexual structure of the basidiomycetes. However, the circuit integrating these events to ensure subsequent sporulation is unclear. Here, we show the spatiotemporal coordination of meiosis and basidial maturation by visualizing event-specific molecules in developing basidia defined by a quantitative approach. Monitoring of gene induction timing together with genetic analysis reveals co-regulation of the coordinated events by a shared regulatory program. Two RRM family regulators, Csa1 and Csa2, are crucial components that bridge meiosis and basidial maturation, further determining sporulation. We propose that the regulatory coordination of meiosis and basidial development serves as a determinant underlying the production of infectious meiospores in C. neoformans.

Elucidation of the determinant for orchestration of solo unisexual cycle in an important human fungal pathogen

“…Our results demonstrated that the removal of α identity genes did not markedly impair unisexual filamentation and the expression level of mCherry-tagged Cfl1 in unisexual communities, which is an indicator protein for filamentous development reported previously (Figure 1D) [35]. Similarly, in the α-null mutant, no detectable defect was identified during basidial maturation, based on the basidial maturation score (BMS) assay that allow us to quantitatively evaluate basidial maturation (Figure 1E) [16]. In addition, we showed that the α sex-determination system did not appear to impact meiosis during unisexual reproduction, since the simultaneous deletion of the α sex-determination genes cannot cause evident changes in the spatiotemporal expression of Dmc1 (a meiosis-specific recombinase), a meiosis indicator protein that is highly abundant during meiotic progression (Figure 1F) [36].…”

“…To identify the regulon of Vea2, we utilized a high-coverage strand-specific RNA-sequencing analysis to compare whole-genome expression between wild-type and the vea2 Δ mutant at 12 hours after sexual induction, when a majority of genes responsible for early sexual events (such as syngamy) are induced based on our previous study [16]. We identified 54 protein-coding genes that displayed markedly altered expression in the absence of Vea2 (Table S2, log 2 |fold-change| > 1.0, q value < 0.01, TPM (transcripts per million mapped) > 5).…”

“…Genes reported previously to control unisexual development are denoted in black, whereas genes that we newly deleted in XL280α are denoted in red. Transcriptional dynamics for each TF during unisexual development were based on the RNA sequencing data reported in the previous XL280α sexual reproduction paper [16].…”

“…Data are presented as the mean ± SD of six independent experiments, two-tailed Student’s t -test. (G) The overlap between CQS2 -regulated genes revealed by RNA-seq analysis of the CQS2 overexpression strain and PUM1 -controlled genes, which were identified based on the published RNA-seq data targeting the PUM1 OE strain [16]. Fisher’s exact test.…”

“…A subpopulation of aerial hyphae subsequently differentiates to form sexual structure (basidia) at their tips. Basidial differentiation occurs concomitantly with meiotic progression, ultimately leading to the production of four spore-chains from the basidium apex [16, 21]. These processes in unisexual and bisexual reproduction are controlled by gene networks with similar architectures.…”