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Specific interaction of an RNA-binding protein is critical to oomycete sexual reproduction

Oomycetes are a class of eukaryotic microorganisms with life cycles and growth habits similar to filamentous fungi, but are not true fungi. Although sexual reproduction, which produce oospores, is an essential stage of life cycle, the functions of critical regulators in this biological process remain unclear due to a lack of genome editing technologies and functional genomic studies in oomycetes.
Reproductive Structures of the Phytophthora. The asexual (A) sporangia, (B) zoospores, and (C) chlamydospores, and the sexual (D) oospores.


Oomycetes is a fascinating class of eukaryotic microorganisms that bear resemblance to filamentous fungi. However, they are not true fungi. While their life cycles and growth habits mirror those of fungi, there is still much to uncover about these enigmatic creatures.

One crucial aspect of Oomycete biology is sexual reproduction. It plays a pivotal role in their life cycle, yet the precise functions of critical regulators involved in this biological process have remained elusive. A major factor for this knowledge gap is the lack of advanced genome editing technologies and functional genomic studies in Oomycetes. However, recent groundbreaking research has begun to shed light on these mysteries.

In a pioneering study conducted by Dr. Feng and colleagues, they delved into the secrets of Pythium ultimum, a notorious Oomycete pathogen responsible for causing various diseases in a wide range of plant species. By developing the first-ever CRISPR/Cas9 system-mediated gene knockout and in situ complementation methods specifically for Pythium, the researchers made significant strides in understanding the factors influencing Oomycete sexual reproduction.

During their investigations, the research team identified two major functional factors in Pythium ultimum: the Puf family RNA-binding protein PuM90 and the flavodoxin-like protein PuFLP. These proteins emerged as key players in oospore formation, an essential process in Oomycete sexual reproduction. Notably, the researchers proposed an intriguing model wherein PuM90 acts as a stage-specific post-transcriptional regulator by selectively binding to the 3′-UTR of PuFLP, subsequently repressing the levels of PuFLP mRNA.

The implications of this study extend beyond Pythium ultimum. The innovative technologies and invaluable data obtained through this research provide a solid foundation for understanding sexual reproduction and post-transcriptional regulation in other Oomycetes as well.

Let’s dive deeper into the findings of this study. When examining Pythium ultimum, the researchers discovered that the absence of PuM90 due to gene knockout resulted in significantly impaired oospore formation. Notably, the mutant oogonia or oospores displayed larger sizes with thinner oospore walls compared to the wild type, indicating the critical role of PuM90 in this reproductive process.

Further investigations revealed the specific interaction between PuM90 and PuFLP. The researchers identified a tripartite recognition motif (TRM) within the Puf domain of PuM90, which exhibited specific binding affinity to a UGUACAUA motif present in the 3′ untranslated region (UTR) of PuFLP mRNA. This interaction played a vital role in repressing PuFLP mRNA levels, ultimately facilitating the oospore formation process.

To validate the significance of this PuM90-PuFLP interaction, the researchers conducted additional experiments. They observed similar phenotypic defects in oospore formation when PuFLP was overexpressed or when key amino acids in the TRM of PuM90 or the 3′-UTR binding site in PuFLP were mutated. These findings firmly established the critical nature of the specific interaction between the RNA-binding protein PuM90 and the 3′-UTR of PuFLP mRNA in the post-transcriptional regulation crucial for the sexual reproduction of Pythium ultimum.

This groundbreaking study, published in PLoS Pathogens, represents a significant leap forward in our understanding of Oomycete biology. By successfully implementing advanced genome editing techniques and deciphering the mechanisms governing sexual reproduction and post-transcriptional regulation in Oomycetes, Dr. Feng and colleagues have opened up new avenues for further exploration in this fascinating field.

These findings not only enhance our knowledge of Oomycete biology but also offer valuable insights into developing strategies for managing diseases caused by Pythium ultimum and related pathogens in various plant species.

To delve deeper into the intricacies of this study, you can refer to the original research article titled “Specific interaction of an RNA-binding protein with the 3′-UTR of its target mRNA is critical to oomycete sexual reproduction,” authored by Feng et al. (2021), published in PLoS Pathogens.

Feng H, Wan C, Zhang Z, Chen H, Li Z, Jiang H, et al. (2021) Specific interaction of an RNA-binding protein with the 3′-UTR of its target mRNA is critical to oomycete sexual reproduction. PLoS Pathog 17(10): e1010001. Link to the article


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