Overexpression of gamma-Glutamyl Cyclotransferases 2;1 (CsGGCT2;1)
Reduces Arsenic Toxicity and Accumulation in Camelina sativa (L.)
Abstract
Environmental arsenic contamination adversely affects human health, and
its accumulation diminishes food quality. Glutathione (GSH) is known to
bind and detoxify arsenic and other toxic metals. GSH homeostasis in
living cells is maintained via γ-glutamyl cycle. Previously, γ-glutamyl
cyclotransferases ( GGCTs) have been shown to be involved in GSH
degradation in plants and increasing tolerance to toxic metals. Here we
characterized the GGCT2;1 homolog from Camelina sativa for
its role in arsenic tolerance and accumulation. Overexpressing
CsGGCT2;1 in Camelina resulted in strong tolerance to arsenite
(AsIII). Compared to wild-type, overexpression (OE) lines had
significantly higher shoot (2.6-3.5-fold) and root (7-10-fold) biomass
on AsIII containing media and accumulated 40-60% less arsenic in root
and shoot tissues. Further, OE lines had higher chlorophyll content,
lower lipid peroxidation and oxidative stress. There was a small but
nonsignificant increase in 5-oxoproline (5-OP) in OE lines and the
upregulation of Oxoprolinase 1 ( OXP1) suggested
accelerated conversion of 5-OP to glutamate, which is then utilized for
GSH resynthesis for maintaining homeostasis. Overall, overexpression of
GGCT2;1 and it homologs in Camelina and other crops will enable their
cultivation on contaminated marginal lands to reduce As accumulation,
addressing food safety issues as well as future food and biofuel needs.