# ABA and Pre-Harvest Sprouting Differences in Knockout Lines of OsPHS3 Encoding Carotenoid Isomerase via CRISPR/Cas9 in Rice

## TL;DR

This paper shows how knocking out the OsPHS3 gene in rice affects plant growth and increases pre-harvest sprouting, offering insights into similar crops.

## Contribution

The study reveals novel molecular mechanisms of pre-harvest sprouting in rice through OsPHS3 gene knockout and carotenoid pathway analysis.

## Key findings

- OsPHS3 knockout lines showed reduced plant height, panicle length, and seed weight but increased pre-harvest sprouting.
- KO lines had higher expression of PSY1, PSY2, and PDS genes but lower ε-LCY, β-LCY, and ZEP1 transcripts.
- Carotenoid and ABA levels decreased in knockout lines compared to wild-type rice.

## Abstract

We generated and characterized knockout mutant lines of the OsPHS3 gene using the CRISPR/Cas9 system. The knockout lines of the OsPHS3 gene showed that 1 bp and 7 bp deletion, early termination codons were used for protein production. Agronomic characteristics of knock-out lines were reduced in plant height, culm diameter, panicle length, seed size and weight, except for the number of tillers. In addition, we analyzed the expression levels of carotenoid biosynthesis genes by qRT-PCR. Among the genes encoding carotenoid metabolic pathway enzymes, the level of transcripts of PSY1, PSY2, PSY3, PDS and ZDS were higher in the KO lines than in the WT line. In contrast, transcription of the ε-LCY, β-LCY and ZEP1 genes were downregulated in the KO lines compared to the WT line. Also, the KO lines decreased carotenoid content and ABA amount compared to WT, while preharvest sprouts increased. These results suggested that they would certainly help explain the molecular mechanisms of PHS in other crops, such as wheat and barley, which are susceptible to PHS.