Replicating minichromosomes as a new tool for plastid genome engineering.

Plant molecular farming, that is, using plants as hosts for production of therapeutic proteins and high-value compounds, has gained substantial interest in recent years. Chloroplasts in particular are an attractive subcellular compartment for expression of foreign genes. Here, we present a new method for transgene introduction and expression in chloroplasts that, unlike classically used approaches, does not require transgene insertion into the chloroplast genome.

Salicylic acid is involved in the Nb-mediated defense responses to Potato virus X in Solanum tuberosum.

To evaluate the role of salicylic acid (SA) in Nb-mediated hypersensitive resistance to Potato virus X (PVX) avirulent strain ROTH1 in Solanum tuberosum, we have constructed SA-deficient transgenic potato plant lines by overexpressing the bacterial enzyme salicylate hydroxylase (NahG), which degrades SA. Evaluation of these transgenic lines revealed hydrogen peroxide accumulation and spontaneous lesion formation in an age- and light-dependent manner. In concordance, NahG potato plants were more sensitive to treatment with methyl viologen, a reactive oxygen species-generating compound.

NRG1, a CC-NB-LRR protein, together with N, a TIR-NB-LRR protein, mediates resistance against tobacco mosaic virus.

In animals and plants, innate immunity is regulated by nucleotide binding domain and leucine-rich repeat (NB-LRR) proteins that mediate pathogen recognition and that activate host-cell defense responses. Plant NB-LRR proteins, referred to as R proteins, have amino-terminal domains that contain a coiled coil (CC) or that share similarity with animal Toll and interleukin 1 receptors (TIR). To investigate R protein function, we are using the TIR-NB-LRR protein N that mediates resistance against tobacco mosaic virus (TMV) through recognition of the TMV p50 protein.

High throughput virus-induced gene silencing implicates heat shock protein 90 in plant disease resistance.

Virus-induced gene silencing was used to assess the function of random Nicotiana benthamiana cDNAs in disease resistance. Out of 4992 cDNAs tested from a normalized library, there were 79 that suppressed a hypersensitive response (HR) associated with Pto-mediated resistance against Pseudomonas syringae. However, only six of these clones blocked the Pto-mediated suppression of P.

Virus-induced gene silencing in plants.

Virus-induced gene silencing (VIGS) is a technology that exploits an RNA-mediated antiviral defense mechanism. In plants infected with unmodified viruses the mechanism is specifically targeted against the viral genome. However, with virus vectors carrying inserts derived from host genes the process can be additionally targeted against the corresponding mRNAs.

Ubiquitin ligase-associated protein SGT1 is required for host and nonhost disease resistance in plants.

Homologues of the yeast ubiquitin ligase-associated protein SGT1 are required for disease resistance in plants mediated by nucleotide-binding site/leucine-rich repeat (NBS-LRR) proteins. Here, by silencing SGT1 in Nicotiana benthamiana, we extend these findings and demonstrate that SGT1 has an unexpectedly general role in disease resistance. It is required for resistance responses mediated by NBS-LRR and other R proteins in which pathogen-derived elicitors are recognized either inside or outside the host plant cell.