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Arthrobotrys oligospora (Arthrobotrys oligospora) is a representative nematode-preying fungus that can produce a sticky three-dimensional mesh (predator organ) to kill nematodes.
Autophagy is a widespread degradation process in eukaryotic cells.
When cells encounter various external stresses, they will initiate autophagy to maintain the stability of the internal environment, thereby ensuring the normal proliferation and differentiation of cells.
However, little is known about the function of autophagy in nematode-eater fungi.
Recently, Science China Life Sciences published an online research paper entitled "AoATG5 plays pleiotropic roles in vegetative growth, cell nucleus development, conidiation, and virulence in the nematode-trapping fungus Arthrobotrys oligospora", revealing the new functions of the autophagy gene AoATG5 .
The first author of this article is Zhou Duanxu, a doctoral student at the State Key Laboratory of Conservation and Utilization of Biological Resources in Yunnan, jointly established by the provincial and ministerial departments of Yunnan University.
The corresponding authors are Professor Zhang Keqin and Researcher Yang Jinkui of Yunnan University.
The study found that the sequence similarity of the autophagy protein AoAtg5 encoded by the AoATG5 gene to Atg5 homologous to other filamentous fungi is 31.
5-42.
5%, and the sequence similarity to Saccharomyces cerevisiae Atg5 is 27.
1%.
Knock out the AoATG5 gene, the growth rate of the hyphae of the mutant strain (ΔAoATG5) in different media decreased, the aerial hyphae decreased, the number of conidial stems decreased, the yield of conidia decreased significantly, and some key sporulation genes (such as The expression levels of abaA, brlA and wetA) were significantly down-regulated.
Arthrobotrys oligosporum is a multi-nucleated filamentous fungus.
The number of nuclei in the hyphal cells of the wild-type (WT) strain is 10-20, and the number of nuclei in the hyphal cells of the mutant strain is 1-9.
RT-PCR analysis found that the expression levels of some genes related to nuclear development in the mutant strains were significantly up-regulated, including h1 and rad25 genes.
At the same time, transcriptome analysis found that the transcription level of genes related to the mycelial cell nucleus was significantly up-regulated in mutant strains, including genes related to DNA repair, synthesis and ligation, but the expression levels of genes related to nucleotide synthesis and metabolism were significantly down-regulated.
(figure 1).
Figure 1.
Comparison of nuclear and related gene transcription levels between wild-type (WT) strains and ΔAoATG5 mutant strains.
A.
DAPI staining to observe the mycelial cell nucleus.
The red arrow indicates the cell membrane; the white arrow indicates the cell nucleus.
B.
Comparison of the number of nuclei.
C.
Compared with the relative transcription level of genes related to DNA synthesis, repair and ligation.
* Indicates p <0.
05 (ΔAoATG5 vs.
WT).
D.
Under the induction of nitrogen deficiency, GO enrichment analysis of differentially expressed genes related to DNA recombination, nucleotide metabolism and synthesis.
URD is an up-regulated gene, and DRD is a down-regulated gene (ΔAoATG5 vs.
WT).
The autophagy process was studied by constructing a GFP-Atg8 fusion protein.
Under the induction of nitrogen deficiency, the GFP-Atg8 signal was mainly distributed in the vegetative hyphae of the WT strain and the vacuoles of the predatory organ cells, while the mutant strain hyphae and the predatory organ cells There is almost no GFP-Atg8 signal in the vacuole.
Further transmission electron microscopy showed that the mycelial vacuoles of the WT strain contained more autophagosomes, while the mycelial vacuoles of the mutant strains contained almost no autophagosomes (Figure 2), indicating autophagy The transport and degradation of the body is blocked in the mutant strain.
Nematode induction experiments found that the number of predatory organs produced by mutant strains was significantly reduced.
At the same time, most of the predatory organs produced by mutant strains contained only 1-3 mycelial circles, which significantly reduced the ability to kill nematodes.
Figure 2.
Comparison of GFP-Atg8 signal in vegetative hyphae and predator cells of wild-type (WT) strains and ΔAoATG5 mutant strains.
A.
Under the induction of nitrogen starvation, the distribution of GFP-Atg8 autophagy signal in vacuoles of vegetative hyphae; B.
The distribution of GFP-Atg8 autophagy signal in predator cells; the white arrow indicates the position of the vacuole.
C.
Observation of mycelial vacuoles and autophagosomes under a transmission electron microscope.
Transcriptome analysis found that under nitrogen deficiency-induced conditions, differentially expressed genes are mainly enriched in autophagy and autophagy-related processes, including phagocytic vesicle assembly sites, protein metabolism, carbohydrate metabolism and ribosome synthesis, etc.
, and some are related to autophagy.
The transcription level of phagocytosis-related genes was significantly up-regulated.
RT-PCR analysis showed that the transcription level of some autophagy genes was significantly up-regulated in the mutant strain, and the ATG8 gene was up-regulated 3.
16 times.
The above experimental results show that in the case of nutrient deprivation, fungi can recycle nutrients by initiating autophagy to overcome the adverse external environment.
In summary, the study found that the autophagy gene AoATG5 not only participates in the growth, sporulation, and autophagosome formation of Arthrobotrys oligospora; it also participates in the regulation of the number of nuclei, the formation and morphological development of predatory organs, and the ability to kill nematodes.
This study found for the first time that AoATG5 regulates the number of nuclei of nematode-predating fungi, laying a foundation for further elucidating the regulation mechanism of autophagy in the growth, development and differentiation of nematode-predating fungi.
For details of the research, please read the original text▼[click the link below or read the original text] Zhou, D.
, Zhu, Y.
, Bai, N.
, Yang, L.
, Xie, M.
, Yang, J.
, Zhu, M.
, Zhang , KQ, and Yang, J.
(2021).
AoATG5 plays pleiotropic roles in vegetative growth, cell nucleus development, conidiation, and virulence in the nematode-trapping fungus Arthrobotrys oligospora.
Sci China Life Sci 64, https:// doi.
org /10.
1007/s11427-020-1913-9
Autophagy is a widespread degradation process in eukaryotic cells.
When cells encounter various external stresses, they will initiate autophagy to maintain the stability of the internal environment, thereby ensuring the normal proliferation and differentiation of cells.
However, little is known about the function of autophagy in nematode-eater fungi.
Recently, Science China Life Sciences published an online research paper entitled "AoATG5 plays pleiotropic roles in vegetative growth, cell nucleus development, conidiation, and virulence in the nematode-trapping fungus Arthrobotrys oligospora", revealing the new functions of the autophagy gene AoATG5 .
The first author of this article is Zhou Duanxu, a doctoral student at the State Key Laboratory of Conservation and Utilization of Biological Resources in Yunnan, jointly established by the provincial and ministerial departments of Yunnan University.
The corresponding authors are Professor Zhang Keqin and Researcher Yang Jinkui of Yunnan University.
The study found that the sequence similarity of the autophagy protein AoAtg5 encoded by the AoATG5 gene to Atg5 homologous to other filamentous fungi is 31.
5-42.
5%, and the sequence similarity to Saccharomyces cerevisiae Atg5 is 27.
1%.
Knock out the AoATG5 gene, the growth rate of the hyphae of the mutant strain (ΔAoATG5) in different media decreased, the aerial hyphae decreased, the number of conidial stems decreased, the yield of conidia decreased significantly, and some key sporulation genes (such as The expression levels of abaA, brlA and wetA) were significantly down-regulated.
Arthrobotrys oligosporum is a multi-nucleated filamentous fungus.
The number of nuclei in the hyphal cells of the wild-type (WT) strain is 10-20, and the number of nuclei in the hyphal cells of the mutant strain is 1-9.
RT-PCR analysis found that the expression levels of some genes related to nuclear development in the mutant strains were significantly up-regulated, including h1 and rad25 genes.
At the same time, transcriptome analysis found that the transcription level of genes related to the mycelial cell nucleus was significantly up-regulated in mutant strains, including genes related to DNA repair, synthesis and ligation, but the expression levels of genes related to nucleotide synthesis and metabolism were significantly down-regulated.
(figure 1).
Figure 1.
Comparison of nuclear and related gene transcription levels between wild-type (WT) strains and ΔAoATG5 mutant strains.
A.
DAPI staining to observe the mycelial cell nucleus.
The red arrow indicates the cell membrane; the white arrow indicates the cell nucleus.
B.
Comparison of the number of nuclei.
C.
Compared with the relative transcription level of genes related to DNA synthesis, repair and ligation.
* Indicates p <0.
05 (ΔAoATG5 vs.
WT).
D.
Under the induction of nitrogen deficiency, GO enrichment analysis of differentially expressed genes related to DNA recombination, nucleotide metabolism and synthesis.
URD is an up-regulated gene, and DRD is a down-regulated gene (ΔAoATG5 vs.
WT).
The autophagy process was studied by constructing a GFP-Atg8 fusion protein.
Under the induction of nitrogen deficiency, the GFP-Atg8 signal was mainly distributed in the vegetative hyphae of the WT strain and the vacuoles of the predatory organ cells, while the mutant strain hyphae and the predatory organ cells There is almost no GFP-Atg8 signal in the vacuole.
Further transmission electron microscopy showed that the mycelial vacuoles of the WT strain contained more autophagosomes, while the mycelial vacuoles of the mutant strains contained almost no autophagosomes (Figure 2), indicating autophagy The transport and degradation of the body is blocked in the mutant strain.
Nematode induction experiments found that the number of predatory organs produced by mutant strains was significantly reduced.
At the same time, most of the predatory organs produced by mutant strains contained only 1-3 mycelial circles, which significantly reduced the ability to kill nematodes.
Figure 2.
Comparison of GFP-Atg8 signal in vegetative hyphae and predator cells of wild-type (WT) strains and ΔAoATG5 mutant strains.
A.
Under the induction of nitrogen starvation, the distribution of GFP-Atg8 autophagy signal in vacuoles of vegetative hyphae; B.
The distribution of GFP-Atg8 autophagy signal in predator cells; the white arrow indicates the position of the vacuole.
C.
Observation of mycelial vacuoles and autophagosomes under a transmission electron microscope.
Transcriptome analysis found that under nitrogen deficiency-induced conditions, differentially expressed genes are mainly enriched in autophagy and autophagy-related processes, including phagocytic vesicle assembly sites, protein metabolism, carbohydrate metabolism and ribosome synthesis, etc.
, and some are related to autophagy.
The transcription level of phagocytosis-related genes was significantly up-regulated.
RT-PCR analysis showed that the transcription level of some autophagy genes was significantly up-regulated in the mutant strain, and the ATG8 gene was up-regulated 3.
16 times.
The above experimental results show that in the case of nutrient deprivation, fungi can recycle nutrients by initiating autophagy to overcome the adverse external environment.
In summary, the study found that the autophagy gene AoATG5 not only participates in the growth, sporulation, and autophagosome formation of Arthrobotrys oligospora; it also participates in the regulation of the number of nuclei, the formation and morphological development of predatory organs, and the ability to kill nematodes.
This study found for the first time that AoATG5 regulates the number of nuclei of nematode-predating fungi, laying a foundation for further elucidating the regulation mechanism of autophagy in the growth, development and differentiation of nematode-predating fungi.
For details of the research, please read the original text▼[click the link below or read the original text] Zhou, D.
, Zhu, Y.
, Bai, N.
, Yang, L.
, Xie, M.
, Yang, J.
, Zhu, M.
, Zhang , KQ, and Yang, J.
(2021).
AoATG5 plays pleiotropic roles in vegetative growth, cell nucleus development, conidiation, and virulence in the nematode-trapping fungus Arthrobotrys oligospora.
Sci China Life Sci 64, https:// doi.
org /10.
1007/s11427-020-1913-9
