Identification of eukaryotic translation initiation factors and the temperature-dependent nature of Turnip mosaic virus epidemics in allopolyploid Brassica juncea

Abstract

Eukaryotic translation initiation factors (eIFs) are essential protein complexes involved in the translation of mRNA into proteins. These initiation factors are generally used as targets in the control of plant RNA virus infections. In the present study, we identified a total 190 eIFs, clustered phylogenetically into 40 distinct subfamilies in the allopolyploid Brassica juncea. Extensive evolutionary duplications of the eIFs in B. juncea suggest their increased genetic diversity and wide adaptability. The induction of expressions in some of the eIFs after inoculation against Turnip mosaic virus (TuMV) provided candidate targets to be used in the control of viral infections. In addition, the expression profiles of eIFs under different temperatures suggested that the TuMV epidemic was temperature dependent. The eIFs expressions suggested that the systemic viral infections were more acute in plants grown between 20 °C and 28 °C. In addition, our results revealed that new subgroups of eIFs, eIF2β, eIF2α, eIF2Bβ, EF1A, and PABP could be represented as targets for antiviral strategies in B. juncea. In summary, our findings would be helpful in studying the complex mechanisms of eIF-mediated, temperature-dependent RNA virus control in B. juncea.

Resistance to Turnip Mosaic Virus in the Family Brassicaceae

“…A similar conclusion was reached from an analysis of Arabidopsis plants from a transposon insertion library in which an eIF(iso)4E mutant line was identified and shown to be resistant to TuMV and the potyvirus lettuce mosaic virus (Duprat et al, 2002). These studies led to testing genes encoding eIF4E, eIF(iso)4E, as well as other eukaryotic translation factors, of other plant species, as candidate recessive resistance genes (reviewed by Shopan et al, 2020aShopan et al, , 2020b. Another study also showed that an Arabidopsis mutant line with a mutation in eIF(iso)4E was unable to support infection by TuMV, but supported infection by the potyvirus clover yellow vein virus, while an Arabidopsis mutant line with a mutation in eIF4E was able to support infection by TuMV, but not clover yellow vein virus (Sato et al, 2005).…”

“…Arabidopsis was shown to contain several genes for resistance to TuMV, some of which have been cloned, while others represent possible candidate genes that could be explored for mapping and evaluation in syntenic crop species, such as brassicas or radish. The identification of genes expressing translation factors [eIF(iso)4E and others] in Arabidopsis, which confer recessive resistance to TuMV and other potyviruses has led to such genes being sought out as candidate resistance genes in various crops (reviewed by Shopan et al, 2020aShopan et al, , 2020b. In addition, various laboratories have developed novel forms of resistance against TuMV, by, intragenic (genes from related and sexually compatible species), cisgenic (genes from related but sexually incompatible species) or transgenic means; the last using expression of either TuMV sequences to induce RNA silencing, or other genes from various sources, usually in a model system, but also in brassica.…”

Characterization and Mapping of retr04, retr05 and retr06 Broad-Spectrum Resistances to Turnip Mosaic Virus in Brassica juncea, and the Development of Robust Methods for Utilizing Recalcitrant Genotyping Data

“…The only BjueIFs suggested in the chromosome A06 QTL associated with TWBJ20 were BjuA022587 and BjuA023685 ; these are both proposed by Shopan et al (2020) to be homologs of eIF2ß . Of these two putative eIF2ß genes, BjuA023685 was also contained within the A06 QTL associated with TWBJ14 resistance.…”

“…As with retr01 -based resistance in B. rapa , it is possible that eIF4E/eIF(iso)4E allelic variants (which TuMV cannot use) could be candidates for retr04 , retr05 , and retr06 . Shopan et al (2020) used sequence data of 95 established eukaryotic translation initiation factors ( eIFs ) from Arabidopsis thaliana to identify homologs across various Brassica species, including 190 putative B. juncea eIFs ( BjueIFs ). Using the positions of these BjueIFs on the B. juncea cv.…”

“…While BjueIFs suggested in these QTLs may represent candidates for retr04 , retr05 , and retr06 , the B. juncea cv. Tumida genome assembly employed by Shopan et al (2020) may not accurately represent e IF variation in germplasm explored here. Future analyses of putative e IF s using the unpublished B. juncea reference assembly based on the specific 060DH17 line used in this study may elucidate if these e IF s are likely candidate resistance genes of interest.…”