Methods
Plasmid construction and P. tricornutum transfection
Plasmid pBHR68 [25] was used as template for amplification
of phaA, phaB and phaC genes from R. eutropha
H16. For in vivo localization studies sequences were
cloned upstream to the eGFP (enhanced green fluorescent
protein) sequence into the vector pPha-NR, which
is a derivative of pPhaT1 with endogenous nitrate
reductase promoter/terminator flanking the multiple
cloning site [GenBank:JN180663]. The inducible nitrate
reductase promoter system was established earlier in the
diatom C. fusiformis by Poulsen et al. 2005 [26]. Transfection
proceeded as described previously [27] with the
exception that cells were grown under non-induced conditions
with NH4
+ as sole nitrogen source. For PHB
synthesis in P. tricornutum, the sequence for phaC was
cloned into the vector pPha-NR (not containing eGFP),
and sequences of phaA and phaB were inserted into the
vector pPha-DUAL[2xNR], which is a pPha-NR derivative
with two multiple cloning sites both under the control
of endogenous nitrate reductase promoter
[GenBank:JN180664]. Both plasmids were mixed and
co-transfected under non-induced conditions.