Phosphoribosylamidotransferase, the first enzyme for purine de novo synthesis, is required for conidiation in the sclerotial mycoparasite Coniothyrium minitans.

Li Qin, Xiaoyan Gong, Jiatao Xie, Daohong Jiang, Jiasen Cheng, Guoqing Li, Junbin Huang, Yanping Fu

State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, Hubei Province, China.

Fungal genetics and biology : FG & B 2011 Oct

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Coniothyrium minitans is an important sclerotial parasite of the fungal phytopathogen, Sclerotinia sclerotiorum. Previously, we constructed a T-DNA insertional library, and screened for many conidiation-deficient mutants from this library. Here, we report a T-DNA insertional mutant ZS-1T21882 that completely lost conidiation. In mutant ZS-1T21882, the T-DNA was integrated into a gene (CmPrat-1) which encodes phosphoribosylamidotransferase (PRAT, EC 2.4.2.14), an enzyme catalyzing the first committed step in de novo purine nucleotide synthesis. Gene replacement and complementation experiments confirmed that phosphoribosylamidotransferase is essential for conidiation of C. minitans. Mutant ZS-1T21882 did not grow on modified Czapek-Dox broth (MCD), but it grew well on MCD amended with IMP or AMP. The conidial production of this mutant was dependent on the dosage of IMP amended. At low concentrations, such as 0.1 mM and 0.25 mM, the mutant produced very few pycnidia, while up to 0.75 mM or higher, the conidiation of this mutant was restored completely. cAMP could not restore the conidiation of mutant ZS-1T21882 when amended into MCD, but could when amended into PDA. Neither GMP nor cGMP could restore the conidiation in MCD or in PDA. Our findings suggest that phosphoribosylamidotransferase is essential for conidiation of C. minitans via adenosine related molecules. Furthermore, when dual cultured with its host, this mutant produced conidia in the host mycelium and on the sclerotia of S. sclerotiorum, but not in dead mycelium or on dead sclerotia, suggesting that C. minitans is likely to able to obtain adenosine or related components from its host during parasitization. Copyright © 2011 Elsevier Inc. All rights reserved.

Citation

Li Qin, Xiaoyan Gong, Jiatao Xie, Daohong Jiang, Jiasen Cheng, Guoqing Li, Junbin Huang, Yanping Fu. Phosphoribosylamidotransferase, the first enzyme for purine de novo synthesis, is required for conidiation in the sclerotial mycoparasite Coniothyrium minitans. Fungal genetics and biology : FG & B. 2011 Oct;48(10):956-65