Summary auto-generated
This study examined how the whitefly Bemisia tabaci acquires tomato yellow leaf curl virus (TYLCV) using Southern blot analysis to detect viral DNA in individual insects. Researchers exposed whiteflies to TYLCV-infected tomato plants for varying periods and measured viral DNA accumulation. Detection frequency increased with feeding duration, reaching 15% of insects after 30 minutes and 100% after 8 hours. Insects feeding on young leaves with high virus content acquired detectable virus within 2 hours, while those on older leaves required 8 hours. Notably, insects feeding on low-virus plants acquired similar viral DNA amounts as those on high-virus plants, suggesting selective feeding on virus-rich cells. Whiteflies accumulated a maximum of approximately 600 million viral genomes (1 nanogram of DNA), indicating a saturation mechanism. Viruliferous insects retained TYLCV DNA for at least 13 days when placed on uninfected plants. The viral DNA in whiteflies appeared as single-stranded genomic DNA, with no evidence of viral replication in the insect vector. These findings demonstrate that TYLCV acquisition is not passive virus ingestion but involves complex virus-insect interactions with regulated upper limits on viral accumulation.
Key findings
- TYLCV DNA was detected in whiteflies after 30 minutes of feeding, with detection rates increasing to 100% by 8 hours of access to infected plants
- Whiteflies acquired similar amounts of viral DNA from low-virus and high-virus plants, suggesting they selectively feed on virus-rich cells rather than passively ingesting virus proportional to plant virus content
- Whiteflies accumulated a maximum of approximately 600 million TYLCV genomes (1 nanogram DNA), indicating a saturation mechanism that limits viral accumulation in the insect vector
- Young leaves with high virus content allowed whiteflies to acquire detectable virus within 2 hours, while older leaves required 8 hours, highlighting the importance of tissue developmental stage
- Viruliferous whiteflies retained TYLCV DNA for at least 13 days on uninfected plants, with no evidence of viral replication occurring within the insect vector
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Abstract
Tomato yellow leaf curl virus (TYLCV) genomic DNA can be detected by Southern blot analysis in nucleic acid extracted from a single whitefly. Acquisition of TYLCV by individual whiteflies in relation to the length of the access period, the virus concentration in, and the developmental stage of plant tissues was studied. The frequency of TYLCV detection increased with the length of the access-period; DNA was detected in 15% of whiteflies tested after a period of access to infected tissue of 30 min, regardless of whether it had a high or a low virus content (5 ng or 0.05 ng TYLCV DNA/micrograms plant chromosomal DNA), and in all insects tested after an 8 h period of access to all the plants. Those insects which had access to the youngest leaves of source plants, which have a high virus content, acquired detectable TYLCV DNA within 2 h. Insects which had access to a tissue for the same period acquired variable amounts of TYLCV DNA; insects feeding on plants with a low virus concentration acquired amounts of viral DNA comparable to those acquired by insects feeding on plants containing a 100-fold greater concentration of virus. Viruliferous insects retained TYLCV DNA for at least 13 days when placed on uninfected tomato plants. In these tests, whitefly could not acquire more than 600 million virus genomes (1 ng viral DNA), suggesting the existence of factors controlling the number of virions present in an insect.