Study : Dynamics and Characterization of Small RNAs of Virus and Host Origin from Wheat Streak Mosaic Virus- and/or Triticum Mosaic Virus-infected Susceptible and Temperature-Sensitive Resistant Wheat Cultivars
Dynamics and Characterization of Small RNAs of Virus and Host Origin from Wheat Streak Mosaic Virus- and/or Triticum Mosaic Virus-infected Susceptible and Temperature-Sensitive Resistant Wheat Cultivars
Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) are type members of Tritimovirus and Poacevirus genera, respectively, in the family Potyviridae, and are transmitted by wheat curl mites. Co-infection of these two viruses causes synergistic interaction with increased virus accumulation and disease severity in wheat. In this study, we examined the effects of synergistic interaction between WSMV and TriMV on endogenous small (s) RNAs and virus-specific small interfering RNAs (vsiRNAs) in susceptible (Arapahoe) and temperature-sensitive resistant (Mace) wheat cultivars at 27ºC and 18ºC. Single- and double-infections in wheat caused a shift in the profile of endogenous sRNAs from 24 nt being the most predominant in healthy plants to 21 nt in infected wheat. Additionally, we report high-resolution vsiRNA maps of WSMV and TriMV in singly- and doubly-infected wheat cultivars Arapahoe and Mace at 18ºC and 27ºC. Massive amounts of 21 and 22 nt vsiRNA reads were accumulated in Arapahoe at both temperatures and in Mace at 27ºC but not at 18ºC. The plus- and minus-sense vsiRNAs were distributed throughout the genomic RNAs in Arapahoe at both temperature regimens and in Mace at 27ºC, although some regions of genomic RNAs serve as hot-spots with an excessive number of vsiRNAs. The positions of vsiRNA peaks were conserved among wheat cultivars Arapahoe and Mace, suggesting that Dicer-like enzymes of susceptible and resistant wheat cultivars are similarly accessed the genomic RNAs of WSMV and TriMV. Additionally, several cold-spot regions were found in the genomes of TriMV and WSMV with no or a few vsiRNAs, indicating that certain regions of WSMV and TriMV genomes are not accessible to Dicer-like enzymes. The high-resolution map of endogenous and vsiRNAs from wheat cultivars synergistically infected with WSMV and TriMV at two temperature regimens form a foundation for understanding the virus-host interactions, effect of synergistic interactions on host defense mechanisms, and virus resistance mechanisms in wheat. Overall design: Small RNA was sequenced from two wheat cultivars (Mace and Araphahoe), at two temperatures 18ºC and 27ºC, for healthy (control/uninfected), infected with wheat streak mosaic virus (WSMV), infected with Triticum mosaic virus (TriMV), and a double-infecttion of WSMV and TriMV.