Modulation of class III peroxidase pathways and phenylpropanoids in Arundo donax under salt and phosphorus stress

Arundo donax L. is an invasive species that has been recently employed for biomass production due to its well-known ability to colonize harsh environment. Based on previous observations, the present study investigated the potential role of phenylpropanoids and class III peroxidases to confer adaptation through biochemical and transcriptomic analysis in A. donax after Na⁺ and P excess supply, both in single stress and in combination, and after growth at low P level. The levels of hydrogen peroxide, flavonoids (i.e., quercetin, apigenin and kaempferol derivatives) and the activity of class III peroxidases, as well as the expression of several genes encoding for their enzymes involved in their biosynthesis, increased when Na⁺ was supplied in combination with P. These results suggest that those biomolecules are involved in the response of A. donax, to the presence of +Na and P in the soil. Moreover, even though at the sampling time no significant accumulation of lignin has been determined, the trend of accumulation of such metabolite and most of all the increase of several transcripts involved in its synthesis was found. This work for the first time indicates the need for further investigation devoted to elucidating whether the strengthening of cell walls via lignin synthesis is one of the mechanisms used by A. donax to adapt to harsh environments.

The interaction of Lolium latent virus major coat protein with ankyrin repeat protein NbANKr redirects it to chloroplasts and modulates virus infection

The Lolium latent virus (LoLV) major coat protein sequence contains a typical chloroplast transit peptide (cTP) domain. In infected Nicotiana benthamiana leaf tissue, LoLV coat proteins can be detected at the chloroplast. In transient expression, several N-terminal deletions of the CP sequence, increasing in length, result in disruption of the domain functionality, markedly affecting intracellular localization. A yeast two-hybrid-based study using LoLV CP as bait identified several potentially interacting Arabidopsis host proteins, most of them with chloroplast-linked pathways. One of them, an ankyrin repeat protein, was studied in detail. The N. benthamiana homologue (NbANKr) targets chloroplasts, is able to co-localize with LoLV CP at chloroplast membranes in transient expression and shows a robust interaction with LoLV CP in vivo by BiFC, which has been confirmed by yeast two-hybrid data. Silencing NbANKr genes in N. benthamiana plants, prior to challenging with LoLV by mechanical inoculation, affects LoLV infection, significantly reducing the level of viral RNA in young leaves, compared to levels in control plants, and suggesting an inhibition of virus movement. Silencing of NbANKr has no obvious effect on plant phenotype, but is able to interfere with LoLV infection, opening the way for a new strategy for virus infection control.

The complete genome sequence of polygonum ringspot virus

The complete genome sequence of polygonum ringspot virus (PolRSV), genus Tospovirus, family Bunyaviridae, was determined. This is the first report of the complete genome sequence for a European tospovirus isolate. The large RNA of PolRSV was 8893 nucleotides (nt) in size and contained a single open reading frame of 8628 nucleotides in the viral-complementary sense, coding for a predicted RNA-dependent RNA polymerase of 330.9 kDa. Two untranslated regions of 230 and 32 nucleotides were present at the 5' and 3' termini, respectively, which showed conserved terminal sequences, as commonly observed for tospovirus genomic RNAs. The medium and small (S) RNAs were 4710 and 2485 nucleotides in size, respectively, and showed 99 % homology to the corresponding genomic segment of a previously partially characterized PolRSV isolate, Plg3. Protein sequences for GN/GC, N and NSs were identical in length in the two PolRSV isolates, while an amino acid insertion was observed for the NSm protein of the newly characterized isolate. The noncoding intergenic region of the S RNA was very short (183 nt) and was not predicted to form a hairpin structure, confirming that this unique characteristic within tospoviruses, previously observed for Plg3, is not isolate specific.