The phytopathogenic virulent effector protein RipI induces apoptosis in budding yeast Saccharomyces cerevisiae.
Virulent protein toxins secreted by the bacterial pathogens can cause cytotoxicity by various molecular mechanisms to combat host cell defense. On the other hand, these proteins can also be used as probes to investigate the defense pathway of host innate immunity. Ralstonia solanacearum, one of the most virulent bacterial phytopathogens, translocates more than 70 effector proteins via type III secretion system during infection. Here, we characterized the cytotoxicity of effector RipI in budding yeast Saccharomyce scerevisiae, an alternative host model. We found that over-expression of RipI resulted in severe growth defect and arginine (R) 117 within the predicted integrase motif was required for inhibition of yeast growth. The phenotype of death manifested the hallmarks of apoptosis. Our data also revealed that RipI-induced apoptosis was independent of Yca1 and mitochondria-mediated apoptotic pathways because Δyca1 and Δaif1 were both sensitive to RipI as compared with the wild type. We further demonstrated that RipI was localized in the yeast nucleus and the N-terminal 1-174aa was required for the localization. High-throughput RNA sequencing analysis showed that upon RipI over-expression, 101 unigenes of yeast ribosome presented lower expression level, and 42 GO classes related to the nucleus or recombination were enriched with differential expression levels. Taken together, our data showed that a nuclear-targeting effector RipI triggers yeast apoptosis, potentially dependent on its integrase function. Our results also provided an alternative strategy to dissect the signaling pathway of cytotoxicity induced by the protein toxins.
School of Life Sciences and Biomedical Center, Sun Yat-sen University, No. 135 Xingang Road West, Guangzhou 510275, China.
Meng-Ying
MY
Deng
School of Life Sciences and Biomedical Center, Sun Yat-sen University, No. 135 Xingang Road West, Guangzhou 510275, China.
Yun-Hao
YH
Sun
School of Life Sciences and Biomedical Center, Sun Yat-sen University, No. 135 Xingang Road West, Guangzhou 510275, China.
Pai
P
Li
School of Life Sciences and Biomedical Center, Sun Yat-sen University, No. 135 Xingang Road West, Guangzhou 510275, China.
Bei
B
Fu
School of Life Sciences and Biomedical Center, Sun Yat-sen University, No. 135 Xingang Road West, Guangzhou 510275, China.
Dong
D
Shen
School of Life Sciences and Biomedical Center, Sun Yat-sen University, No. 135 Xingang Road West, Guangzhou 510275, China. Electronic address: luyj@mail.sysu.edu.cn.
Yong-Jun
YJ
Lu
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000502:physiology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D059014:High-Throughput Nucleotide Sequencing; D043368:Ralstonia solanacearum / Q000472:pathogenicity*; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics / Q000254:growth & development; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000378:metabolism
D001426:Bacterial Proteins
Apoptosis; Effector protein; RNA-seq; Ralstonia solanacearum; RipI; Saccharomyces cerevisiae