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Plant virus or viroid infection stimulates the phosphorylation of a plant-encoded protein of M, 68,000 to 70,000 (now termed pPKR) that is associated with double-stranded RNA-stimulated protein kinase activity. Using various biochemical and immunological comparisons, we have demonstrated that this plant protein is an analog of the mammalian PKR enzymes. pPKR is both cytosolic and ribosome associated, similar to mammalian PKR, and appears to be capable of phosphorylating exogenous histones. Monoclonal antiserum to the human PKR as well as antiserum to a conserved double-stranded RNA-binding domain present on mammalian PKR demonstrated cross-reactivity with pPKR. Likewise, polyclonal antiserum to the pPKR detected the mouse and human PKR in western blot analysis. Northern blot analysis of a mammalian PKR cDNA detected a specific 2.5-kb transcript present in plant poly(A)' RNA.

Regulation of protein synthesis by eukaryotic initiation factor-2alpha (eIF-2alpha) phosphorylation is a highly conserved phenomenon in eukaryotes that occurs in response to various stress conditions. Protein kinases capable of phosphorylating eIF-2alpha have been characterized from mammals and yeast. However, the phenomenon of eIF2-alpha-mediated regulation of protein synthesis and the presence of an eIF-2alpha kinase has not been demonstrated in higher plants. We show that plant eIF-2alpha (peIF-2alpha) and mammalian eIF-2alpha (meIF-2alpha) are phosphorylated similarly by both the double-stranded RNA-binding kinase, pPKR, present in plant ribosome salt wash fractions and the meIF-2alpha kinase, PKR. By several criteria, phosphorylation of peIF-2alpha is directly correlated with pPKR protein and autophosphorylation levels. Significantly, pPKR is capable of specifically phosphorylating Ser51 in a synthetic eIF-2alpha peptide, a key characteristic of the eIF-2alpha kinase family. Taken together, these data support the concept that pPKR is a member of the eIF-2alpha kinase family. In addition, the inhibition of brome mosaic virus RNA in vitro translation in wheat germ lysates by the addition of double-stranded RNA, phosphorylated peIF-2alpha, meIF-2alpha, or activated human PKR suggests that plant protein synthesis may be regulated via phosphorylation of eIF-2alpha.

BackgroundProliferation and expansion of security risks necessitates new measures to ensure authenticity and validation of GMOs. Watermarking and other cryptographic methods are available which conceal and recover the original signature, but in the process reveal the authentication information. In many scenarios watermarking and standard cryptographic methods are necessary but not sufficient and new, more advanced, cryptographic protocols are necessary.ResultsHerein, we present a new crypto protocol, that is applicable in broader settings, and embeds the authentication string indistinguishably from a random element in the signature space and the string is verified or denied without disclosing the actual signature. Results show that in a nucleotide string of 1000, the algorithm gives a correlation of 0.98 or higher between the distribution of the codon and that of E. coli, making the signature virtually invisible.ConclusionsThis algorithm may be used to securely authenticate and validate GMOs without disclosing the actual signature. While this protocol uses watermarking, its novelty is in use of more complex cryptographic techniques based on zero knowledge proofs to encode information.

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