Lecture 11 &12Lecture 11 &12

Virus resistant plantsVirus resistant plants

Expression of Expression of dsRNase(RNaseIII)dsRNase(RNaseIII)• wheat engineered to express the E. coli gene for wheat engineered to express the E. coli gene for

ribonuclease (RNase) IIIribonuclease (RNase) III• most plant viruses have double-stranded RNA most plant viruses have double-stranded RNA • a mutant of RNase III was useda mutant of RNase III was used• the mutant enzyme able to bind to double-the mutant enzyme able to bind to double-

stranded RNAstranded RNA• introduced into wheat, under the control of a corn introduced into wheat, under the control of a corn

ubiquitin gene (Fig. 4), by micro- projectile ubiquitin gene (Fig. 4), by micro- projectile bombardmentbombardment

• transgenic plants resistance to infection by transgenic plants resistance to infection by barley stripe mosaic virusbarley stripe mosaic virus

Genetic construct used to transform wheat Genetic construct used to transform wheat plantsplantswith the gene for the mutant form of E. coli with the gene for the mutant form of E. coli RNase III. The construct includes the maize RNase III. The construct includes the maize ubiquitin promoter, first exon and intron in ubiquitin promoter, first exon and intron in front of a mutant form of E. coli RNase III and front of a mutant form of E. coli RNase III and a transcription terminator region from a a transcription terminator region from a nopaline synthase genenopaline synthase gene

Expression of antiviral Expression of antiviral proteinsproteins• pokeweed (Phytolacca americana) -3 antiviral pokeweed (Phytolacca americana) -3 antiviral

proteins in its cell wall proteins in its cell wall • pokeweed antiviral protein PAPI-in spring leaves; pokeweed antiviral protein PAPI-in spring leaves; • PAPII-in summer leaves; and PAP-S-in seedsPAPII-in summer leaves; and PAP-S-in seeds• Both PAP and PAPII are ribosome-inactivating Both PAP and PAPII are ribosome-inactivating

proteins proteins • remove a specific adenine residue from the large remove a specific adenine residue from the large

ribosomal RNA ribosomal RNA • pokeweed plants infected with viruses, either PAP pokeweed plants infected with viruses, either PAP

or PAPII is synthesizedor PAPII is synthesized• PAP and PAP II are good candidates for developing PAP and PAP II are good candidates for developing

transgenic plants resistant to a broad spectrum of transgenic plants resistant to a broad spectrum of plant virusesplant viruses