Functional conservation of EXA1 among diverse plant species for the infection by a family of plant viruses

Abstract

Since the propagation of plant viruses depends on various host susceptibility factors, deficiency in them can prevent viral infection in cultivated and model plants. Recently, we identified the susceptibility factor Essential for poteXvirus Accumulation 1 ( EXA1 ) in Arabidopsis thaliana , and revealed that EXA1-mediated resistance was effective against three potexviruses. Although EXA1 homolog genes are found in tomato and rice, little is known about which viruses depend on EXA1 for their infection capability and whether the function of EXA1 homologs in viral infection is conserved across multiple plant species, including crops. To address these questions, we generated knockdown mutants using virus-induced gene silencing in two Solanaceae species, Nicotiana benthamiana and tomato. In N . benthamiana , silencing of an EXA1 homolog significantly compromised the accumulation of potexviruses and a lolavirus, a close relative of potexviruses, whereas transient expression of EXA1 homologs from tomato and rice complemented viral infection. EXA1 dependency for potexviral infection was also conserved in tomato. These results indicate that EXA1 is necessary for effective accumulation of potexviruses and a lolavirus, and that the function of EXA1 in viral infection is conserved among diverse plant species.

Abscisic Acid Connects Phytohormone Signaling with RNA Metabolic Pathways and Promotes an Antiviral Response that Is Evaded by a Self-Controlled RNA Virus

“…Consistent with these studies, results of our phosphoproteomic meta-analysis revealed ABA-dependent responsiveness of the phosphorylation status of host components that regulate RNA stability, turnover, maturation, and translation initiation. These included (1) factors known to be needed for potyvirus (eIFiso4G1, but not eIFiso4G2) or potexvirus infection (EXA1) ( Nicaise et al, 2007 ; Yusa et al, 2019 ); (2) regulators of the emerging antiviral pathway of RNA decay, such as those involved in mRNA decapping (i.e., VCS and VCR) and 5′-3′ mRNA decay (XRN2, XRN3, LARP1A); (3) determinants of mRNA turnover, such as UBP1C, PUM2, PUM4, and TUDOR-SN PROTEIN 2 (TSN2); and (4) components necessary for mRNA splicing, including coilin, a protein recently linked to SA signaling activation in response to virus infection ( Mäkinen et al, 2017 ; Chantarachot and Bailey-Serres, 2018 ; Li and Wang, 2019 ; Shaw et al, 2019 ; Xu et al, 2020 ).…”

Plantago asiatica mosaic virus: An emerging plant virus causing necrosis in lilies and a new model RNA virus for molecular research

“…EXA1 orthologs are found in a wide range of plant species, including tomato, rice, and N. benthamiana , and knockdown of EXA1 orthologs in tomato and N. benthamiana significantly reduced the accumulation of potexviruses and the related lolavirus. This restriction of viral infection is cancelled by complementation with the rice EXA1 gene, indicating that the proviral function of EXA1 is conserved among a wide range of plants (Yusa et al, 2019). However, the effect of EXA1 knockdown in N. benthamiana on virus accumulation differs depending on virus species, suggesting that EXA1 paralogs function redundantly in a virus‐specific manner.…”

Complete Genome Sequence of Clover Yellow Mosaic Virus Isolated from White Clover in Japan

“…To obtain full-length cDNA from ClYMV-JPN-2021, reverse transcription was conducted using GeneRacer oligo(dT) primer (Invitrogen, USA), which hybridizes the 3′ poly(A) tail of the potexvirus genome. PCR was performed on the cDNA using a ClYMV 1F primer designed on the 5′-end sequence determined by 5′ RACE and a KpGR3nest primer designed on the GeneRacer oligo(dT) primer ( 12 ). The amplified ClYMV-JPN-2021 genome was inserted into the pPPVOu binary vector ( 13 ) as described previously ( 12 ), and six clones were sequenced by primer walking using the primers listed in Table 1 .…”

“…PCR was performed on the cDNA using a ClYMV 1F primer designed on the 5′-end sequence determined by 5′ RACE and a KpGR3nest primer designed on the GeneRacer oligo(dT) primer ( 12 ). The amplified ClYMV-JPN-2021 genome was inserted into the pPPVOu binary vector ( 13 ) as described previously ( 12 ), and six clones were sequenced by primer walking using the primers listed in Table 1 . Using ATGC v4.3.5 software (Genetyx, Japan), all sequence reads from the six clones were trimmed and assembled into a single contig with 100% identity in each of the overlapping regions.…”