Recent progress has shown that vacuolar Pi transporters (VPTs) are
important for cellular Pi homeostasis against external Pi variations in
Arabidopsis and rice, while it is poorly understood for the identity and
regulatory mechanism of VPTs in Brassica napus ( B.
napus). Here, we identified two vacuolar Pi influx transporters
BnA09PHT5;1b and BnCnPHT5;1b in B. napus and uncovered their
necessity for cellular Pi homeostasis through functional analysis.
BnPHT5;1bs are the homologs of Arabidopsis AtPHT5;1 with the similar
sequence, structure, tonoplast localization, and VPT activity.
BnPHT5;1b double mutants had smaller shoot growth and higher
shoot cellular Pi than the wild-type B. napus, which are largely
different from the report in At PHT5;1 mutant, suggesting
PHT5;1-VPTs play a distinct mechanism of cellular Pi homeostasis in
seedlings of B. napus and Arabidopsis. By contrast,
disruption of BnPHT5;1b genes slowed vegetative growth
accompanied by Pi toxicity in floral organs, reduced seed yield and
impacted seed traits, agreeing with the role of AtPHT5;1 in floral Pi
homeostasis. Taken together, our studies identified two vacuolar Pi
influx transporters in B. napus and revealed the distinct and
conserved regulatory mechanisms of BnPHT5;1bs in cellular Pi homeostasis
in this plant species.