Scientists from University of Lleida-Agrotecnio Center and partners aimed to
alter the starch biosynthetic machinery of
[www.isaaa.org] rice
using CRISPR-Cas9 to introduce mutations affecting the Waxy (Wx) locus
encoding granule-bound starch synthase I (GBSSI) in rice endosperm. Mutation
of genes in the starch biosynthetic pathway has a significant impact on
starch quality and quantity.

CRISPR-Cas9 mutations lead to the reduction, but not elimination of the GBSS
activity in the seeds. It was reported that the GBSS activity in the mutants
was 61-71% of wild-type levels, similarly to two irradiation mutants, but
the amylose content was reduced to 8-12% in heterozygous seeds and to as low
as 5% in homozygous seeds. Abnormal cellular organization in the aleurone
layer and amorphous starch grain structures were also observed. The
expression of other genes involved in starch production was modulated in
seeds and leaves, which resulted in the changes in AGPase and sucrose
synthase activity which explained the corresponding starch and soluble sugar
concentrations.

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