eIF2Bβ confers resistance to Turnip mosaic virus by recruiting ALKBH9B to modify viral RNA methylation

Abstract

Eukaryotic translation initiation factors (eIFs) are the primary targets for overcoming RNA virus resistance in plants. In a previous study, we mapped a BjeIF2Bβ from Brassica juncea representing a new class of plant virus resistance genes associated with resistance to Turnip mosaic virus (TuMV). However, the mechanism underlying eIF2Bβ-mediated virus resistance remains unclear. In this study, we discovered that the natural variation of BjeIF2Bβ in the allopolyploid B. juncea was inherited from one of its ancestors, B. rapa. By editing of eIF2Bβ, we were able to confer resistance to TuMV in B. juncea and in its sister species of B. napus. Additionally, we identified an N⁶-methyladenosine (m⁶A) demethylation factor, BjALKBH9B, for interaction with BjeIF2Bβ, where BjALKBH9B co-localized with both BjeIF2Bβ and TuMV. Furthermore, BjeIF2Bβ recruits BjALKBH9B to modify the m⁶A status of TuMV viral coat protein RNA, which lacks the ALKB homologue in its genomic RNA, thereby affecting viral infection. Our findings have applications for improving virus resistance in the Brassicaceae family through natural variation or genome editing of the eIF2Bβ. Moreover, we uncovered a non-canonical translational control of viral mRNA in the host plant.