Characterization of cucumber mosaic virus (CMV) subgroup IB infecting chilli in Tamil Nadu, India

Engineering resistance against Cucumber mosaic virus in Nicotiana tabacum through virus derived transgene expressing hairpin RNA

Cucumber mosaic virus (CMV) is the one of notorious virus known for its ubiquitous nature and causes substantial yield loss worldwide. The resistance against the Cucumber mosaic virus (CMV) was envisaged in Nicotiana tabacum transgenic lines by introducing viral gene fragments. The chimeric hairpin RNA constructs incorporating 401 bp of coat protein, 411 bp of replicase protein and 361 bp of 2b gene were developed respectively and transformed into N. tabacum. The regenerated transgenic lines introduced with inverted repeats of CMV gene fragments exhibited enhanced resistance against CMV. The preliminary molecular screening and qPCR confirmed the integration of transgene in the transgenic lines. The spectrum of resistance in transgenic lines was evaluated by challenge inoculation with CMV and the resistance was determined through DAC-ELISA. The complete resistance was achieved in the hpRNA-CP transformant with a very low titre (0.029) of CMV followed by hpRNA-REP (0.099) with no symptoms.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03576-1.

Arabidopsis Tetraspanins Facilitate Virus Infection via Membrane-Recognition GCCK/RP Motif and Cysteine Residues

Tetraspanins (TETs) function as key molecular scaffolds for surface signal recognition and transduction via the assembly of tetraspanin-enriched microdomains. TETs' function in mammalian has been intensively investigated for the organization of multimolecular membrane complexes, regulation of cell migration and cellular adhesion, whereas plant TET studies lag far behind. Animal and plant TETs share similar topologies, despite the hallmark of "CCG" in the large extracellular loop of animal TETs, plant TETs contain a plant specific GCCK/RP motif and more conserved cysteine residues. Here, we showed that the GCCK/RP motif is responsible for TET protein association with the plasma membrane. Moreover, the conserved cysteine residues located within or neighboring the GCCK/RP motif are both crucial for TET anchoring to membrane. During virus infection, the intact TET3 protein enhanced but GCCK/RP motif or cysteine residues-deficient TET3 variants abolished the cell-to-cell movement capability of virus. This study provides cellular evidence that the GCCK/RP motif and the conserved cysteine residues are the primary determinants for the distribution and function of TET proteins in Arabidopsis.

Co-existence of chlorosis inducing strain of Cucumber mosaic virus with tospoviruses on hot pepper (Capsicum annuum) in India

Cucumo- and tospoviruses are the most destructive viruses infecting hot pepper (chilli). A diagnostic survey was conducted to assess the prevalence of cucumo and tospoviruses in chilli growing tracts of Tamil Nadu. Infected plants showing mosaic with chlorotic and necrotic rings, veinal necrosis, mosaic mottling, leaf filiformity and malformation were collected. Molecular indexing carried out through reverse transcription polymerase chain reaction (RT-PCR) with coat protein gene specific primer of Cucumber mosaic virus (CMV) and tospovirus degenerate primer corresponding to the L segment (RdRp). Ostensibly, amplifications were observed for both CMV and tospoviruses as sole as well for mixed infections. The sequence analysis indicated that the Capsicum chlorosis virus (CaCV) and Groundnut bud necrosis virus (GBNV) to be involved with CMV in causing combined infections. The co-infection of CMV with CaCV was detected in 10.41% of the symptomatic plant samples and combined infection of CMV with GBNV was recorded in around 6.25% of the symptomatic plants surveyed. The amino acid substitution of Ser¹²⁹ over conserved Pro¹²⁹ in coat protein of CMV implies that CMV strain involved in mixed infection as chlorosis inducing strain. Further, the electron microscopy of symptomatic plant samples explicated the presence of isometric particles of CMV and quasi spherical particles of tospoviruses. This is the first molecular evidence for the natural co-existence of chlorosis inducing CMV strain with CaCV and GBNV on hot pepper in India.