Scientists from Nanjing Agricultural University used CRISPR-Cas9 to enhance pre-harvest sprouting resistance in rice.

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 genes that 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.

The preprint version of the article is published in Research Square.