Scientists from Nanjing Agricultural University used CRISPR-Cas9to
enhance pre-harvest sprouting resistance inrice.

Pre-harvest sprouting in cereal crops is a universal phenomenon that
impacts grain yield and quality. Breeders have been applying various
techniques, including genome editing, to fortify seed dormancy and
prevent pre-harvest sprouting.

Previous studies have shown that abscisic acid (ABA) is one of the
phytohormones that promote seed dormancy. Thus, the genesthat encode
abscisic acid 8' hydroxylase, which catabolizes ABA, are vital in seed
dormancy. Only a few knockout versions of/OsABA8ox/have been developed
to improve seed dormancy. To enhance rice pre-harvest sprouting
resistance, the researchers developed a technique using CRISPR-Cas9
editing to generate new/OsABA8oxs/mutant lines with increased levels of
seed dormancy in the background of elite, high-yielding japonica variety
Ningjing6, which often sprouts before harvest under high temperature and
rainy conditions.

Six transgenic mutant lines were developed and were evaluated for three
years through molecular identification of target genes, monitoring of
major agronomic traits, and several physiological and biochemical
indicators. The knock-out/OsABA8ox/genes, particularly/OsABA8ox1/,
significantly strengthened seed dormancy and improved pre-harvest
spouting resistance. Results of analyses suggested that improved ABA
signaling caused stronger dormancy. When the same gene was knocked out
in other varieties, similar results were generated, which may imply that
genetic modification of the/OsABA8ox1/gene has potential for application
in breeding.

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