Abstract
Plastids (chloroplasts) possess an enormous capacity to synthesize
and accumulate foreign proteins. Here we have maximized chloroplast
protein production by over-expressing a proteinaceous antibiotic
against pathogenic group A and group B streptococci from the plastid
genome. The antibiotic, a phage lytic protein, accumulated to enormously
high levels (>70% of the plant's total soluble protein), and proved
to be extremely stable in chloroplasts. This massive over-expression
exhausted the protein synthesis capacity of the chloroplast such
that the production of endogenous plastid-encoded proteins was severely
compromised. Our data suggest that this is due to translational rather
than transcriptional limitation of gene expression. We also show
that the chloroplast-produced protein antibiotic efficiently kills
the target bacteria. These unrivaled expression levels, together
with the chloroplast's insensitivity to enzymes that degrade bacterial
cell walls and the elimination of the need to remove bacterial endotoxins
by costly purification procedures, indicate that this is an effective
plant-based production platform for next-generation antibiotics,
which are urgently required to keep pace with rapidly emerging bacterial
resistance.
Users
Please
log in to take part in the discussion (add own reviews or comments).