Flowering time is a critical determinant of crop adaptation to local
environments. Maize has spread over a wide latitudinal cline in the Americas
due to its reduced photoperiod sensitivity to adapt to regions over 90° of
latitude.

The team of Cheng Huang from China Agricultural University aimed to explain
how maize adapts to environments above 90° of latitude. The team found that
ZmCCT9 regulates flowering under the long days, allowing maize to adapt to
higher latitudes. Using CRISPR-Cas9, the team knocked-out ZmCCT9 in maize to
further analyze its role.

Analysis of the generated mutants revealed that the gene knockout caused
early flowering under long days. Further analysis also found that ZmCCT9
negatively regulates the expression of the florigen ZCN8, resulting in late
flowering under long days.

These findings help explain how the maize genome with enable maize to adapt
over 90° of latitude.

[www.pnas.org]