O-Acetylserine(thiol)lyase (OASTL) enzyme catalyzes the cysteine biosynthes
is in photosynthetic organisms. In mature Arabidopsis thaliana the highest
activity level is observed in non-photosynthetic tissues like roots, that a
lso show significant amount of protein detected by Western blot analysis. B
y means of specific probes for cytosolic and plastidic OASTL isoenzyme tran
scripts, cytosolic isoenzyme has been determined to be predominantly expres
sed in roots, while the expression of the plastidic isoform is high in both
green and non-green tissues.
Sulfur starvation produces an increase on the OASTL activity level in all t
he Arabidopsis organs examined, this effect being particularly significant
in the aerial parts of the plant.