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Sri Lankan cassava mosaic virus (SLCMV), the primary pathogen responsible for cassava mosaic disease in cassava plantations, is transmitted via infected cutting stems and the whitefly vector, Bemisia tabaci. To obtain better insights into the defense mechanism of cassava against SLCMV, whiteflies were used to induce SLCMV infection for activating the salicylic acid (SA) signaling pathway, which triggers the innate immune system. The study aimed to investigate the specific interactions between viruliferous whiteflies and SA accumulation in resistant (C33), tolerant (Kasetsart 50; KU50), and susceptible (Rayong 11) cassava cultivars by infecting with SLCMV. Leaf samples were collected at various time points, from 1 to 7 days after inoculation (dai). The SA levels were quantified by gas chromatography–mass spectrometry and validated by quantitative reverse transcription polymerase chain reaction. The SA levels increased in KU50 and C33 plants at 2 and 3 dai, respectively, but remained undetected in Rayong11 plants. The expression of PR-9e, PR-7f5, SPS1, SYP121, Hsf8, and HSP90 increased in infected C33 plants at 4 dai, whereas that of KU50 plants decreased immediately at 2 dai, and that of Rayong11 plants increased at 1 dai but gradually decreased thereafter. These findings strongly indicate that SA plays a crucial role in regulating antiviral defense mechanisms, especially in SLCMV-resistant plants. Altogether, the findings provide valuable insights into the mechanisms underlying the activation of SA-mediated anti-SLCMV defense pathways, and the resistance, tolerance, and susceptibility of cassava, which can aid future breeding programs aimed at enhancing SLCMV resistance. [ABSTRACT FROM AUTHOR]

Eighty-five plant species growing near cassava fields were collected and tested by PCR for the presence of begomoviruses and AC1 and AV1 gene of Sri Lankan cassava mosaic virus (SLCMV). This survey revealed that three Euphorbiaceae species, Cnidoscolus chayamansa, Jatropha curcas, and J. multifida, were infected by SLCMV and had mosaic, yellowing, and leaf curling, similar to the symptoms observed on cassava. DNA from the three plant species was analyzed using rolling circle amplification, then Illumina sequencing; the sequences obtained by de novo assembly had high similarity with those of SLCMV of cassava from Southeast Asia. [ABSTRACT FROM AUTHOR]

Helper component proteinases (HC-Pro) are multifunctional potyvirus proteins involved in transmission of polyproteins by aphids. HC-Pro functions include suppression of antiviral RNA silencing and interfering with host symptom expression. Affinity purification-mass spectrometry was used in the present study of in vitro interactions between a recombinant Papaya ringspot virus HC-Pro protein and 23 papaya proteins extracted from the leaves of healthy and virus-infected papaya and identified by liquid chromatography-tandem mass spectrometry. Ten of the identified proteins were found to be involved in plant defense mechanisms (lipoxygenase and TIR-NBS disease resistance-like protein), photosynthesis (bisphosphate carboxylase large chain and red chlorophyll catabolite reductase), transcription (reverse transcriptase), translation (chromosome associate protein subunit h), signal transduction (membrane protein and calcium-dependent lipid-binding-like protein) and carbohydrate metabolism (sucrose-UDP glucosyltransferase and β-1,4-mannosyltransferase). In addition, the interactions between Papaya ringspot virus HC-Pro protein and host proteins may not only provide a better understanding of how viruses replicate and cause disease, but also help elucidate the molecular mechanisms underlying its various functions. [ABSTRACT FROM AUTHOR]