Aarhus University's Inger B. Holme and colleagues from various research
institutions used TALEN- and CRISPR-Cas9-induced mutations to study the
barley phytase gene HvPAPhy_a. The team aimed to validate the PAPhy_a enzyme
as the main contributor of the mature grain phytase activity (MGPA), as well
as the importance of a promoter region of the gene containing GCN4, Skn1 and
the RY elements, known to be involved in gene expression during grain
filling.

The results confirm that the barley PAPhy_a enzyme is the main contributor
to MGPA since the grains from the knock-out lines exhibited very low MGPA.
Lines with mutations in the HvPAPhy_a promoter region GCN4/Skn1/RY also
showed significantly reduced MGPA, proving its importance for HvPAPhy_a
expression. Mutant grains with very low MPGA showed delayed germination as
compared to grains of wild type barley.

Interestingly, lines with deletions located downstream of the promoter motif
showed even lower MGPA levels, indicating that the GCN4/SKn1/RY motif is not
the only element responsible for the level of PAPhy_a expression during
grain maturation.

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