The genetics of conidiophore pigmentation in Aspergillus nidulans.

Clutterbuck, A. J.

doi:10.1099/00221287-136-9-1731

Cited by 63 publications

(49 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One is, as expected, brlA, but we also found transcripts required for conidium differentiation and integrity (phiA and the hydrophobin coding gene rodA [64,65]) or conidium pigmentation (ivoB and ivoC [66,67]). It would be interesting to know why pigmentation genes such as yA are downregulated at this stage and ivoB or ivoC is upregulated.…”

Section: Resultssupporting

confidence: 86%

“…It would be interesting to know why pigmentation genes such as yA are downregulated at this stage and ivoB or ivoC is upregulated. It has been described that the expression of the phenol oxidase-coding transcript ivoB increases with the levels of its substrate N-acetyl-6-hydroxytryptophan (AHT) (67). The increase in ivoC expression is delayed approximately 4 h with respect to that of ivoB (66) (see Table S2 in the supplemental material).…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Transcriptional Changes in the Transition from Vegetative Cells to Asexual Development in the Model Fungus Aspergillus nidulans

et al. 2013

View full text Add to dashboard Cite

cMorphogenesis encompasses programmed changes in gene expression that lead to the development of specialized cell types. In the model fungus Aspergillus nidulans, asexual development involves the formation of characteristic cell types, collectively known as the conidiophore. With the aim of determining the transcriptional changes that occur upon induction of asexual development, we have applied massive mRNA sequencing to compare the expression pattern of 19-h-old submerged vegetative cells (hyphae) with that of similar hyphae after exposure to the air for 5 h. We found that the expression of 2,222 (20.3%) of the predicted 10,943 A. nidulans transcripts was significantly modified after air exposure, 2,035 being downregulated and 187 upregulated. The activation during this transition of genes that belong specifically to the asexual developmental pathway was confirmed. Another remarkable quantitative change occurred in the expression of genes involved in carbon or nitrogen primary metabolism. Genes participating in polar growth or sexual development were transcriptionally repressed, as were those belonging to the HogA/SakA stress response mitogen-activated protein (MAP) kinase pathway. We also identified significant expression changes in several genes purportedly involved in redox balance, transmembrane transport, secondary metabolite production, or transcriptional regulation, mainly binuclear-zinc cluster transcription factors. Genes coding for these four activities were usually grouped in metabolic clusters, which may bring regulatory implications for the induction of asexual development. These results provide a blueprint for further stage-specific gene expression studies during conidiophore development.

show abstract

Section: Resultssupporting

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Transcriptional Changes in the Transition from Vegetative Cells to Asexual Development in the Model Fungus Aspergillus nidulans

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Mutants in brlA form aerial stalks that fail to differentiate vesicles, metulae, phialides or spores (Clutterbuck, 1969). They also fail to express many genes associated with later stages of conidiophore development (Zimmermann e t al., 1980;Boylan e t al., 1987;Adams e t al., 1988;Mirabito et al, 1989;Clutterbuck, 1990;Stringer et al, 1991 ;Timberlake, 1991 I. S K R O M N E , 0.…”

Section: Introductionmentioning

confidence: 99%

Starvation stress modulates the expression of the Aspergillus nidulans brlA regulatory gene

Skromne

Sánchez

Aguirre³

1995

Microbiology

135

122

View full text Add to dashboard Cite

Expression of the Aspergillus nidulans brlA gene plays a fundamental role in the switch from vegetative growth to asexual reproduction. Using a mediashifting protocol to induce submerged SpOrUlatiOn and brlA-lacZ as an expression marker, it was shown that carbon and nitrogen starvation stress induced brlA transcription to different degrees. Glucose starvation induced brlA rapidly to high levels and resulted in spore formation on reduced conidiophores, whereas nitrogen starvation induced brlA gradually to lower levels and sporulation occurred to a lesser extent but from more complex conidiophores. 19-Galactosidase activity paralleled brlAa and mRNA. No clear qualitative differences between the two brlA transcripts were found in these starvation conditions, suggesting that the different patterns of sporulation could be explained by quantitative expression differences. Since brlA mRNA did not accumulate in the presence of a high glucose concentration, we investigated the role of other carbon sources on brlA expression. Nonrepressing carbon sources such as glycerol, acetate and arabinose were as effective as glucose in preventing brlA mRNA accumulation, suggesting that the glucose effects on brlA expression could be explained as a response to nutrient starvation, rather than by carbon catabolite repression. Despite similar low levels of brlA transcripts being detected during growth in glucose or non-repressing carbon sources, conidiophores were formed only in medium containing glycerol, acetate or arabinose. When mycelia were not shifted to starvation conditions, sporulation was not observed in standard minimal medium even after glucose was exhausted, unless the medium was buffered. This and other results suggest that strong deviation from external neutral pH partially prevented full induction and/or function of M A .

show abstract

“…In A. nidulans, a mutation in the ygA gene that encodes a transporter produces yellow conidia at high pH and green conidia at low pH (32,33). The defect in melanization of the ygA mutant is likely caused by a deficiency in copper uptake, as the defect can be remediated by the addition of copper (32).…”

mentioning

confidence: 99%

Laccases Involved in 1,8-Dihydroxynaphthalene Melanin Biosynthesis in Aspergillus fumigatus Are Regulated by Developmental Factors and Copper Homeostasis

2013

View full text Add to dashboard Cite

Aspergillus fumigatus produces heavily melanized infectious conidia. The conidial melanin is associated with fungal virulence and resistance to various environmental stresses. This 1,8-dihydroxynaphthalene (DHN) melanin is synthesized by enzymes encoded in a gene cluster in A. fumigatus, including two laccases, Abr1 and Abr2. Although this gene cluster is not conserved in all aspergilli, laccases are critical for melanization in all species examined. Here we show that the expression of A. fumigatus laccases Abr1/2 is upregulated upon hyphal competency and drastically increased during conidiation. The Abr1 protein is localized at the surface of stalks and conidiophores, but not in young hyphae, consistent with the gene expression pattern and its predicted role. The induction of Abr1/2 upon hyphal competency is controlled by BrlA, the master regulator of conidiophore development, and is responsive to the copper level in the medium. We identified a developmentally regulated putative copper transporter, CtpA, and found that CtpA is critical for conidial melanization under copper-limiting conditions. Accordingly, disruption of CtpA enhanced the induction of abr1 and abr2, a response similar to that induced by copper starvation. Furthermore, nonpigmented ctpA⌬ conidia elicited much stronger immune responses from the infected invertebrate host Galleria mellonella than the pigmented ctpA⌬ or wild-type conidia. Such enhancement in eliciting Galleria immune responses was independent of the ctpA⌬ conidial viability, as previously observed for the DHN melanin mutants. Taken together, our findings indicate that both copper homeostasis and developmental regulators control melanin biosynthesis, which affects conidial surface properties that shape the interaction between this pathogen and its host.A spergillus fumigatus is an opportunistic pathogen that causes life-threatening invasive disease in immunocompromised hosts (1). Its asexual spores, named conidia, are the initial source of inocula for infection and are the vehicles for dispersal and survival. Under favorable conditions, conidia break dormancy and grow as elongated, highly polarized hyaline hyphae. Upon achieving competency and exposure to air, hyphae produce aerial conidiophore stalks and develop elaborate multicellular conidiophores that generate chains of melanized uninucleate conidia (2, 3) (Fig. 1A and B). BrlA, a C 2 H 2 zinc finger transcription factor, is the master regulator that controls the initiation of conidiophore development in Aspergillus (4, 5). AbaA and WetA, two other important regulators that function downstream of BrlA, are required for proper progression of conidiation (6). The abaA gene is activated during the middle stage of conidiophore development, while the wetA gene is required for the activation of late conidiation-specific genes.The 1,8-dihydroxynaphthalene (DHN) melanin coating A. fumigatus conidia gives them their characteristic bluish green color (Fig. 1B). Melanin is an amorphous polymer that is produced by a variety of microbes and ...

show abstract

The genetics of conidiophore pigmentation in Aspergillus nidulans.

Cited by 63 publications

References 25 publications

Transcriptional Changes in the Transition from Vegetative Cells to Asexual Development in the Model Fungus Aspergillus nidulans

Transcriptional Changes in the Transition from Vegetative Cells to Asexual Development in the Model Fungus Aspergillus nidulans

Starvation stress modulates the expression of the Aspergillus nidulans brlA regulatory gene

Laccases Involved in 1,8-Dihydroxynaphthalene Melanin Biosynthesis in Aspergillus fumigatus Are Regulated by Developmental Factors and Copper Homeostasis

Contact Info

Product

Resources

About