Study identifies proteins that promote the spread of mosaic virus.

Researchers have identified two sugarcane proteins that facilitate the replication of sugarcane mosaic virus (SCMV). The study indicates that the small heat shock proteins ScHSP17.5 and ScHSP17.9A interact with the viral protein P3N-PIPO and amplify the accumulation of the pathogen in susceptible plants. The results suggest new targets for genetic improvement programs.

The study compared two contrasting genotypes. The susceptible cultivar Badila showed a peak in viral replication 18 hours after inoculation. The resistant genotype FG1, a somatic mutant derived from Badila, suppressed replication in the first few hours and eliminated the virus up to 192 hours after inoculation.

Absolute quantification revealed a viral load approximately 2.000 times higher in Badila at the peak of infection compared to FG1 during the same period. In Badila leaves, researchers observed typical mosaic symptoms and a high concentration of viral RNA. FG1 did not show detectable symptoms.

Transcriptome analysis at five time points during infection identified over 53 differentially expressed genes. FG1 rapidly activated genes linked to defense, metabolism, and redox regulation. Badila concentrated repressive and delayed changes.

Gene co-expression

Gene co-expression analysis highlighted modules associated with viral load. In FG1, genes linked to reactive oxygen species detoxification and cell signaling gained expression at the critical moment of infection. Among them, ScPER5, ScNAC29, and ScCIPK21 acted as central genes in the network.

In Badila, genes from the small heat shock protein family gained expression during the same period in which the virus reached its highest replication rate. ScHSP17.5 emerged as a central node in the susceptibility-associated module.

Interaction trials

Protein-protein interaction assays confirmed that ScHSP17.5 and ScHSP17.9A interact specifically with the viral movement protein P3N-PIPO. There was no interaction with the capsid protein or with the isolated P3 protein. Functional tests in Nicotiana benthamiana They showed up to a 2,43-fold increase in viral replication when the two sHSPs were co-expressed.

The authors propose that SCMV recruits host heat shock proteins to stabilize viral complexes and promote virus accumulation. In contrast, FG1 activates mechanisms linked to redox regulation and cell signaling early on, thus restricting infection.

More information at doi.org/10.1111/mpp.70229