Fungal, not insect: Revisiting a misidentified Bemisia tabaci protein interacting with a begomovirus coat protein

Abstract

Understanding interactions between viral proteins and those of their biological vectors is essential for elucidating transmission mechanisms and identifying potential targets for disease control. Insect vectors, among the most common and significant transmitters of animal and plant viruses, play a crucial role in viral transmission dynamics. Such interactions can influence virus transmission efficiency and provide insights into how viral diseases spread within ecosystems. Accurate identification of the insect proteins involved is vital, as misidentifications can lead to erroneous conclusions that misguide subsequent research and control strategies. In the case of begomoviruses (Geminiviridae: Begomovirus), a protein previously identified as insect‐derived by Ohnesorge and Bejarano (2009) is shown here, based on the analyses presented in this Commentary, to be of likely fungal origin. This misidentification, based on yeast two‐hybrid and pull‐down experiments, has been repeatedly cited in the literature, perpetuating an incorrect conclusion. Establishing the correct identity of this protein is essential for guiding future research on insect‐virus interactions.

• A small heat‐shock protein (HSP16) previously reported as insect‐derived in Bemisia tabaci actually originates from a fungal species of the genus Wallemia.

• BLAST, genome survey and phylogenetic analyses support the fungal origin and clarify persistent misattribution in the literature.

• Correct identification of this protein is essential to guide future studies on virus–vector interactions and prevent the continued spread of misinformation.

Understanding interactions between viral proteins and those of their biological vectors is essential for elucidating transmission mechanisms and identifying potential targets for disease control. Insect vectors, among the most common and significant transmitters of animal and plant viruses, play a crucial role in viral transmission dynamics. Such interactions can influence virus transmission efficiency and provide insights into how viral diseases spread within ecosystems. Accurate identification of the insect proteins involved is vital, as misidentifications can lead to erroneous conclusions that misguide subsequent research and control strategies. In an early study in aphids, proteins interacting with luteovirus particles were assumed to be of insect origin, and the authors searched the proteinaceous components of the aphid to identify them (van den Heuvel et al., ¹⁹⁹⁴). In that same study, they clarified that one such protein, called symbionin, actually derives from the primary bacterial endosymbiont, a Buchnera sp. Subsequent work established that symbionin corresponds to a homologue of the chaperonin GroEL from Escherichia coli (e.g., Hogenhout et al., ¹⁹⁹⁸), illustrating how early verification can prevent persistent misattribution. In the case of begomoviruses (Geminiviridae: Begomovirus), a protein previously identified as insect‐derived by Ohnesorge and Bejarano (2009) is shown here, based on the analyses presented in this Commentary, to be of likely fungal origin. This misidentification, based on yeast two‐hybrid and pull‐down experiments, has been repeatedly cited in the literature, perpetuating an incorrect conclusion. Establishing the correct identity of this protein is essential for guiding future research on insect–virus interactions.

The family Geminiviridae, a diverse group of plant viruses, comprises 15 genera, of which Begomovirus is the largest (Fiallo‐Olivé et al., 2021). Members are characterized by small, circular, single‐stranded DNA genomes and distinctive geminate virion morphology. Begomovirus represents the largest genus in the virosphere, infecting a broad range of plant hosts, including many economically important crops, and is responsible for significant agricultural losses worldwide (Fiallo‐Olivé & Navas‐Castillo, 2023). Transmission occurs via whiteflies (Hemiptera: Aleyrodidae) of the Bemisia tabaci complex of cryptic species, making understanding vector interactions crucial for mitigating their impact on agriculture.

The study by Ohnesorge and Bejarano (2009) aimed to investigate interactions between the begomovirus coat protein—essential for insect transmission—and proteins from B. tabaci. Yeast two‐hybrid and pull‐down experiments were employed to identify potential protein–protein interactions. A cDNA library from B. tabaci Mediterranean (formerly Q biotype) was constructed in a yeast expression vector, and the gene encoding the tomato yellow leaf curl Sardinia virus (TYLCSV) coat protein was cloned into a separate yeast vector. Co‐transformation of both constructs into yeast cells enabled the identification of candidate interacting protein pairs. While these assays provide evidence of physical interaction, they do not by themselves establish a role in virus transmission, which would require dedicated functional studies.

The results led to the identification of a protein from B. tabaci that interacted with the begomovirus coat protein. This protein was characterized as a small heat‐shock protein (HSP), HSP16, suggesting a potential role for HSPs in begomovirus transmission by whiteflies. The authors proposed that this interaction could provide insights into viral transmission biology and inform strategies to control begomovirus spread. However, genomic sequencing advances indicate that the identified protein likely originates from a fungus present in the whiteflies used to construct the yeast library, rather than from B. tabaci. This misidentification has resulted in a persistent incorrect conclusion in the literature, highlighting the need for correction. It should be noted that, at the time of the original study, complete genome sequences for B. tabaci were not yet available, and fungal sequence databases were much more limited, which likely constrained accurate assignment of the protein's origin.

Several lines of evidence support a fungal, rather than insect, origin for this protein:

1. BLAST analysis. A simple search using the HSP16 sequence reported by Ohnesorge and Bejarano (2009) against public databases reveals no significant matches to B. tabaci sequences. Instead, top hits correspond to the fungal genus Wallemia, suggesting the sequence may not originate from whiteflies. Readers can readily reproduce this observation with a standard BLAST search.

2. Genome survey. A search for this sequence or related homologues across multiple high‐quality B. tabaci genome assemblies (Campbell et al., 2023; Chen et al., ^{2016, 2019}; Xie et al., ²⁰¹⁷) fails to identify any corresponding sequence (results not shown).

3. Phylogenetic analysis. A phylogenetic reconstruction including small HSPs from B. tabaci and Wallemia species demonstrates that the protein clusters robustly within the fungal clade (Figure 1), confirming closer affinity to Wallemia than to whiteflies.

FIGURE 1.

Evolutionary relationships of small heat‐shock protein (HSP) sequences inferred using the Neighbour‐Joining method. The analysis includes HSPs from Bemisia tabaci and Wallemia species. The HSP16 sequence reported by Ohnesorge and Bejarano (2009) is highlighted in bold red. Bootstrap support values (500 replicates) are shown next to the branches. Evolutionary distances were computed using the p‐distance method and are expressed as the number of base differences per site. Analyses were conducted in MEGA12 (Kumar et al., 2024).

The genus Wallemia (Wallemiales: Wallemiaceae) comprises filamentous basidiomycetous fungi that are widely distributed and highly stress‐tolerant, occupying diverse environmental niches (Zajc & Gunde‐Cimerman, 2018). Beyond free‐living habitats, Wallemia species have been reported in insect‐associated contexts, including edible insects such as crickets and locusts (Osimani et al., 2017). More recently, Wallemia spp. were detected in the Mediterranean cryptic species of B. tabaci using metabarcoding approaches, where Wallemia was reported as the most frequent fungal genus in the study (Guo et al., 2023). Collectively, these observations indicate that Wallemia sequences can occur in insect‐derived or insect‐associated samples, making this genus a plausible source of fungal protein sequences detected in such contexts.

A Google Scholar search (accessed on 31 January 2026) returned 69 records citing Ohnesorge and Bejarano (2009), 57 of which are articles published in journals indexed in the Science Citation Index Expanded or in book chapters. Notably, nine citations are from 2023 to 2025, demonstrating that the article continues to be cited. All describe HSP16 as interacting with the TYLCSV coat protein, purportedly originating from the whitefly. By continuing to cite Ohnesorge and Bejarano (2009) as reporting an interaction between a small HSP from B. tabaci and a begomovirus coat protein, this misconception is perpetuated—reinforcing a misinterpretation of the virus–vector relationship and highlighting the need for careful reassessment in future studies.

AUTHOR CONTRIBUTIONS

Jesús Navas‐Castillo: Conceptualization; investigation; writing – original draft. Elvira Fiallo‐Olivé: Conceptualization; investigation; writing – review and editing.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.

Navas‐Castillo, J. & Fiallo‐Olivé, E. (2026) Fungal, not insect: Revisiting a misidentified Bemisia tabaci protein interacting with a begomovirus coat protein. Insect Molecular Biology, 35(4), 361–363. Available from: 10.1111/imb.70037

DATA AVAILABILITY STATEMENT

Data sharing not applicable to this article as no datasets were generated or analysed during the current study.