Begomoviruses belonging to the family Geminiviridae are plant‐infecting DNA viruses. Begomoviral movement protein (MP) has been reported to be required for virus movement, host range determination, and symptom development. In the present study, the FK506‐binding protein (FKBP)‐type peptidyl‐prolyl cis ‐ trans isomerase (NbFKPPIase) of Nicotiana benthamiana was identified by a yeast two‐hybrid screening system using the MP of tomato leaf curl New Delhi virus (ToLCNDV) oriental melon (OM) isolate (MP ^OM ) as bait. Transient silencing of the gene encoding NbFKPPIase increased replication of three test begomoviruses, and transient overexpression decreased viral replication, indicating that NbFKPPIase plays a role in defence against begomoviruses. However, infection of N. benthamiana by ToLCNDV‐OM or overexpression of the gene encoding MP ^OM drastically reduced the expression of the gene encoding NbFKPPIase. Fluorescence resonance energy transfer analysis revealed that MP ^OM interacted with NbFKPPIase in the periphery of cells. Expression of the gene encoding NbFKPPIase was induced by salicylic acid but not by methyl jasmonate or ethylene. Moreover, the expression of the gene encoding NbFKPPIase was down‐regulated in response to 6‐benzylaminopurine and up‐regulated in response to gibberellin or indole‐3‐acetic acid, suggesting a role of NbFKPPIase in plant development. Transcriptome analysis and comparison of N. benthamiana transient silencing and overexpression of the gene encoding MP ^OM led to the identification of several differentially expressed genes whose functions are probably associated with cell cycle regulation. Our results indicate that begomoviruses could suppress NbFKPPIase‐mediated defence and biological functions by transcriptional inhibition and physical interaction between MP and NbFKPPIase to facilitate infection.

Transgenic approaches employing RNA interference (RNAi) strategies have been successfully applied to generate desired traits in plants; however, variations between RNAi transgenic siblings and the ability to quickly apply RNAi resistance to diverse cultivars remain challenging. In this study, we assessed the promoter activity of a cauliflower mosaic virus 35S promoter (35S) and a phloem-specific promoter derived from rice tungro bacilliform virus (RTBV) and their efficacy to drive RNAi against the endogenous glutamate-1-semialdehyde aminotransferase gene (GSA) that acts as a RNAi marker, through chlorophyll synthesis inhibition, and against tomato yellow leaf curl Thailand virus (TYLCTHV), a begomovirus (family Geminiviridae) reported to be the prevalent cause of tomato yellow leaf curl disease (TYLCD) in Taiwan. Transgenic Nicotiana benthamiana expressing hairpin RNA of GSA driven by either the 35S or RTBV promoter revealed that RTBV::hpGSA induced stronger silencing along the vein and more uniformed silencing phenotype among its siblings than 35S::hpGSA. Analysis of transgenic N. benthamiana, 35S::hpTYLCTHV, and RTBV::hpTYLCTHV revealed that, although 35S::hpTYLCTHV generated a higher abundance of small RNA than RTBV::hpTYLCTHV, RTBV::hpTYLCTHV transgenic plants conferred better TYLCTHV resistance than 35S::hpTYLCTHV. Grafting of wild-type (WT) scions to TYLCTHV RNAi rootstocks allowed transferable TYLCTHV resistance to the scion. A TYLCTHV-inoculation assay showed that noninfected WT scions were only observed when grafted to RTBV::hpTYLCTHV rootstocks but not 35S::hpTYLCTHV nor WT rootstocks. Together, our findings demonstrate an approach that may be widely applied to efficiently confer TYLCD resistance.

Understanding the seedborne nature of plant viruses is essential for developing disease control strategies and is impactful to the seed market. Here, we investigated seed transmissibility of tomato leaf curl New Delhi virus-cucumber isolate (ToLCNDV-CB) and -oriental melon isolate (ToLCNDV-OM) in cucumber and seed transmissibility of tomato leaf curl Taiwan virus (ToLCTV) and tomato yellow leaf curl Thailand virus (TYLCTHV) in tomato. Parent plants were inoculated using agroinfiltration with virus infectious clones, and virus infection was confirmed by PCR with virus-specific primers. ToLCNDV-CB and ToLCNDV-OM were detected in different parts of the female and male flowers and the fruits of cucumbers. ToLCNDV-CB and ToLCNDV-OM were also detected in cucumber seed coats and seedlings with an infection rate higher than 79%. Similar results were observed with ToLCTV and TYLCTHV as they were detected in different parts of the female and male flowers and fruits of three tomato cultivars. ToLCTV and TYLCTHV were also detected in tomato seed coats and seedlings with an infection rate higher than 36%. In addition, pollen-mediated transmission assays of these four begomoviruses were conducted with pollen derived from virus-infected plants to healthy plants. Results showed that ToLCNDV-CB and ToLCNDV-OM were detected in cross-pollinated cucumber progenies with an infection rate higher than 70%. ToLCTV and TYLCTHV were also detected in cross-pollinated tomato progenies with an infection rate higher than 77%. Our results indicated that ToLCNDV, ToLCTV, and TYLCTHV can be transmitted via seeds or pollens of cucumber and tomato plants. To our knowledge, this is the first report documenting the pollen-mediated transmission of begomoviruses.

Salicylic acid (SA)-mediated immunity plays important roles in combating virus in plants. Two plant stress associated protein (SAPs) containing dual A20/AN1 zinc-finger domain were found to play important roles in SA-mediated immunity; however, detailed mechanisms remain elusive. In this study, another orchid homolog gene of Pha13 , Pha21 , was analyzed. Pha21 confers antiviral immunity in both transgenic orchid and Arabidopsis overexpressing Pha21. Expression of Pha21 is early-induced by SA treatment, and is involved in the expression of the orchid homolog of the master regulator NPR1 . Pha21 but not Pha13 is involved in the expression of key RNAi-related genes, Dicer-like nuclease 4 ( DCL4 ) and Argonaut 1 ( AGO1 ) in orchids. The involvement of SAPs in expression of orchid DCL4 and AGO1 is not limited to orchid, as AtSAP5 also plays essential role in the expression of Arabidopsis DCL4 and AGO1 . However, unlike Pha13 and AtSAP5, Pha21 does not play positive role in the expression of orchid homolog gene of RNA-dependent RNA polymerase 1 ( RdR1 ), an important gene in RNAi pathway. Pha21 can be found localized in the nucleus, and confers self-E3 ligase and ubiquitin binding activities. Functional domain analysis revealed that both A20 and AN1 domains of Pha21 are required for decreasing virus accumulation, and the AN1 domain plays a more important role in the expression of orchid DCL4 . Collectively, our data suggests SA regulated SAPs play important roles in antiviral immunity and is involved in delicate regulation of key genes in RNAi-mediated pathway. IMPORTANCE: Salicylic acid (SA)-mediated antiviral immunity plays an important role to protect plants from virus infection; however, the detailed mechanisms remain elusive. We previously demonstrated that two plant A20/AN1 proteins, orchid Pha13 and Arabidopsis AtSAP5, function similarly and serve as an important hub to regulate SA-mediated antiviral immunity. In this study, we identified another orchid A20/AN1 protein, Pha21, which is involved in SA-mediated antiviral immunity. In contrast to Pha13 and AtSAP5, Pha21 plays minor negative roles in the expression of PhaRdR1 (orchid homolog of RNA-dependent RNA polymerase 1 ). However, Pha21 and AtSAP5, but not Pha13, are involved in the expression of important players in RNAi pathway, Dicer-like nuclease 4 ( DCL4 ) and Argonaut 1 ( AGO1 ), in orchid and Arabidopsis . Our data demonstrates that plant A20/AN1 proteins are conserved players in SA-mediated antiviral resistance among plants, and provide links between the A20/AN1 proteins and the RNAi pathway.

Murraya exotica L., commonly known as orange jasmine, is an evergreen shrub belonging to the Rutaceae family. It has long been used as traditional Chinese medicine for treating abdominal pain, toot...

Maize, as the global highest-yield grain crop, can impact social stability and security based on its annual yield. Given that maize viruses have caused up to 91% yield reductions, investigating maize virus diseases is of the utmost importance. In July 2020, a suspected maize yellow mosaic virus (MaYMV) was discovered in a maize field, and a MaYMV detection protocol was established. The MaYMV isolate MA70, discovered in a maize plant from Wuri District, Taiwan, in November 2022, was shown to infect both maize 42 days post-inoculation (dpi) and wheat (35 dpi), causing mosaic symptoms, through aphid transmission with corn leaf aphid (Rhopalosiphum maidis). To determine the whole genome sequence of MA70, a 5642 bp sequence was obtained using RT-PCR and Sanger sequencing. Sequencing results indicated a 94.8–96.8% nucleotide sequence similarity with 54 MaYMV isolates from GenBank and with amino acid sequence identities exceeding 90% for all MaYMV proteins. Phylogenetic analysis showed the relationship of MA70 is closest to the Chinese isolate. The nucleotide sequence identity was lower among isolates of more distinct geographical clusters. Between October 2023 and January 2024, survey results indicated that MaYMV prevalence in corn fields across six areas in Taichung reached 17.5% (130/743 plants) and was present in all the sampled fields. MaYMV was present in all sampled fields affirming its ubiquitous presence. This study establishes the first documented case of MaYMV in Taiwan; however, survey findings hint at a potential pre-existing presence in Taiwanese maize fields. Therefore, this research also develops a practical diagnostic tool for field monitoring of MaYMV prevalence, which is crucial for informing future disease management strategies, including the critical need for cross-strait between Taiwan and China collaboration on viral disease surveillance.