Environmental Engineering Reference
In-Depth Information
Se
Se
Se
FIGURE 14.2
Se. luxes. through. plants. growing. in. a. ield.. Plants. can. locally. accumulate. and. change. the.
speciation.of.Se.in.their. adjacent.soil..They.can.accumulate. Se. in.their.roots.and.shoots.and.
assimilate.inorganic.to.organic.Se.in.the.process..They.can.also.volatilize.Se.and.release.it.into.
the.atmosphere.from.their.roots.and.shoots.
Se.volatilization.rate.was.not.affected.in.the.APS.transgenics..Furthermore,.
overexpression.in.
B. juncea
.of.the.irst.enzyme.in.the.conversion.of.SeCys.
to.SeMet,.CgS,.resulted.in.two-.to.threefold.higher.volatilization.rates.com-
pared. to. untransformed. plants. (Van. Huysen. et. al.. 2003).. The. CgS. trans-
genics. accumulated. 40%. less. Se. in. their. tissues. than. wild. type,. probably.
because.of.enhanced.volatilization..The.CgS.transgenics.were.also.more.Se.
tolerant.than.wild-type.plants,.perhaps.due.to.their.lower.tissue.Se.levels.
Another.approach.to.genetically.manipulate.plant.Se.metabolism.focused.
on. the. prevention. of. the. toxicity. caused. by. nonspeciic. SeCys. incorpora-
tion. into. proteins.. In. one. study,. a. mouse. SeCys. lyase. (SL). was. expressed.
in.
Arabidopsis thaliana
. and.
B. juncea
. (Garifullina. et. al.. 2003,. Pilon. et. al..
2003).. This. enzyme. speciically. breaks. down. SeCys. into. alanine. and. ele-
mental.Se..As.expected,.the.SL.transgenics.showed.reduced.Se.incorpora-
tion. into. proteins. (Pilon. et. al.. 2003).. All. the. transgenic. SL. plants. showed.
enhanced. Se. accumulation,. up. to. twofold. compared. to. wild-type. plants..
Similar.results.were.obtained.when.an.
A. thaliana
.homologue.of.the.mouse.
SL.(called.CpNifS).was.overexpressed:.the.CpNifS.transgenics.showed.less.
Se. incorporation. in. proteins. and. twofold. enhanced. Se. accumulation,. as.
well.as.enhanced.Se.tolerance.(Van.Hoewyk.et.al..2005)..In.another.study,.
SMT.from.hyperaccumulator.
A. bisulcatus
.was.overexpressed.in.
A. thaliana
.
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