The
most environmentally abundant bromophenol congener, 2,4,6-tribromophenol
(2,4,6-TBP, 6.06 μmol/L), was exposed to rice for 5 d both in
vivo (intact seedling) and in vitro (suspension cell) to systematically
characterize the fate of its sulfation and glycosylation conjugates
in rice. The 2,4,6-TBP was rapidly transformed to produce 6 [rice
cells (3 h)] and 8 [rice seedlings (24 h)] sulfated and glycosylated
conjugates. The predominant sulfation conjugate (TP408,
93.0–96.7%) and glycosylation conjugate (TP490,
77.1–90.2%) were excreted into the hydroponic solution after
their formation in rice roots. However, the sulfation and glycosylation
conjugates presented different translocation and compartmentalization
behaviors during the subsequent Phase III metabolism. Specifically,
the sulfated conjugate could be vertically transported into the leaf
sheath and leaf, while the glycosylation conjugates were sequestered
in cell vacuoles and walls, which resulted in exclusive compartmentalization
within the rice roots. These results showed the micromechanisms of
the different compartmentalization behaviors of 2,4,6-TBP conjugates
in Phase III metabolism. Glycosylation and sulfation of the phenolic
hydroxyl groups orchestrated by plant excretion and Phase III metabolism
may reduce the accumulation of 2,4,6-TBP and its conjugates in rice
plants.