Strigolactone and karrikin signaling pathways trigger polyubiquitination and degradation of SMXL2 to regulate hypocotyl elongation and gene expression in Arabid

Due to the impaired antiviral RNAi, the dcl2dcl4 (dcl2/4) mutant is highly susceptible to viruses deficient of the viral suppressor of the RNA silencing (VSR) contrast to wild-type Arabidopsis. It was found that more severe disease symptoms were induced in dcl2/4 infected with VSR-deficient CMV (CMV-Δ2b or CMV-2aTΔ2b) compared to wild-type Arabidopsis infected with intact CMV. In order to investigate the underlying mechanism, comparative transcriptome analysis was performed with Col-0 and dcl2/4 that were infected by CMV, CMV-Δ2b and CMV-2aTΔ2b, respectively. Our analysis showed that the systematic infection of CMV, CMV-Δ2b and CMV-2aTΔ2b could cause hypoxia response and reduce photosynthesis. Asymptomatic infections of CMV-Δ2b or CMV-2aTΔ2b in Columbia (Col-0) promoted the expression of cell division-related genes and suppressed the transcription of metabolism and acquired resistance genes. On the other hand, immunity and resistance genes were highly induced, but photosynthesis and polysaccharide metabolism-related genes were suppressed in diseased plants. More interestingly, cell wall reorganization was specifically caused in modestly diseased Col-0 infected by CMV and a strong activation of SA signaling were correspondingly induced in severely diseased dcl2/4 by CMV or CMV mutants. Thus, our research revealed the nature of the Arabidopsis–CMV interaction at the transcriptome level and could provide new clues in symptom development and antiviral defense in plants.

A new virus was found in S. androgynus with curled and yellow leaves in China, andtentatively named as sauropus androgynus virus(SaV). The complete genome of SaV is an 8,007 nucleotides (+) single-stranded RNA excluding a 3’-poly(A) tail, and contains six open reading frames (ORFs). Both pairwise comparisons and phylogenetic analyseswith putative replicase or coat protein show that SaV shares high homology with allexiviruses in the family Alphaflexiviridae. SaV should be the first allexivirus reported in S. androgynus.

Longan witches’ broom-associated virus (LWBaV), a member of the family Potyviridae, possesses a positive-sense single-stranded RNA genome, was first described to infect longan (Dimocarpus longan Lour.) at an experimental greenhouse in Hanoi, Vietnam (Seo et al. 2017). Longan is a tropical fruit tree of the soapberry family (Sapindaceae) and is grown widely in Southeast Asia, including Vietnam, China, and Thailand. Litchi (Litchi chinensis Sonn.), another economically important subtropical soapberry family tree species belonging to the family Sapindaceae, have similar environmental requirements and shares abundant habitat with Longan (Lora et al. 2018). LWBaV was detected in litchi seedlings imported from China in Gimcheon, South Korea in 2024 (Belete et al. 2025). Since litchi plants are cultivated in several provinces of China, including Guangdong, Guangxi, Fujian, Hainan and Taiwan, the region of LWBaV infecting litchi trees in China remains unclear. In December 2025, one litchi plant in the campus of Fujian Agriculture and Forestry University in Fujian, China (26°05′4.35″N, 119°14′21.57″E) exhibited virus disease-like symptoms, including leaf deformation, shoot proliferation, and shortened internodes. To identify the causal agent, total RNA was extracted from the symptomatic leaves with CTAB method (Wang and Stegemann, 2010). An rRNA-depleted library was constructed with the diseased litchi total RNA and subjected to high throughput sequencing in PE150 mode on an Illumina NovaSeq 6000 platform at Novogene, China, generating 50.99 million reads. After removing low-quality reads using fastp (version 1.0.1) (Chen 2025), 50.74 million reads were assembled de novo using Trinity (version 2.15.1) with default parameters. Contigs longer than 200 bp were used to search the NCBI non-redundant (NR) protein database using BLASTx to identify possible viral contigs. A total of 489 contigs yielded significant hits against a locally curated viral RefSeq protein database (downloaded on 18 August 2025 from NCBI (https://www.ncbi.nlm.nih.gov/)), with aligned regions exceeding 500 amino acids in length. Among these, a contig of 9,429 bp exhibited notable sequence similarity to LWBaV, which is the only virus like sequence identified in the high throughput sequence data. Subsequent BLASTn analyses revealed that the obtained genomic sequence shared 96.18% and 92.41% nucleotide sequence identity with the isolate Gm1 (PV470486) and isolate Han1 (NC_034835) of LWBaV, respectively. To further verify whether the plants were infected with LWBaV, we designed a primer pair, 8616F/9232R (5’-CGAGTCTTCTTTCCAATATGGAG-3’/5’GGCGGGCCACAGGATATTAATGA-3’) which was used to amplify the 617-bp fragments for the partial sequences of CP in the LWBaV genome. The amplified PCR product was cloned to plasmid and sanger sequenced. The resulting sequence shared 95.62% and 93.52% nucleotide homology with the LWBaV isolate Gm1 (PV470489) and isolate Han1 (NC_034835), respectively. To our best knowledge, this is the first report of LWBaV infecting litchi in Fujian, China, extending the information on its geographical distribution. This finding also lays the foundation for the detection and management strategies of litchi virus diseases.