OsASN1 Plays a Critical Role in Asparagine-Dependent Rice Development

Abstract

Asparagine is one of the important amino acids for long-distance transport of nitrogen (N) in plants. However, little is known about the effect of asparagine on plant development, especially in crops. Here, a new T-DNA insertion mutant, asparagine synthetase 1 (asn1), was isolated and showed a different plant height, root length, and tiller number compared with wild type (WT). In asn1, the amount of asparagine decreased sharply while the total nitrogen (N) absorption was not influenced. In later stages, asn1 showed reduced tiller number, which resulted in suppressed tiller bud outgrowth. The relative expression of many genes involved in the asparagine metabolic pathways declined in accordance with the decreased amino acid concentration. The CRISPR/Cas9 mutant lines of OsASN1 showed similar phenotype with asn1. These results suggest that OsASN1 is involved in the regulation of rice development and is specific for tiller outgrowth.

OsASN1 Overexpression in Rice Increases Grain Protein Content and Yield under Nitrogen-Limiting Conditions

“…Thus, in our field condition, OsASN1 has a limited role in tiller development. In contrast, the mutants showed a reduced growth pattern in consistent with a previous report ( Luo et al. 2018) .…”

“…Characterization of OsASN1 knockout mutants ( Ohashi et al. 2015 , 2018, Luo et al. 2018) were previously reported with some discrepancies.…”

“…Luo et al characterized a T-DNA mutant ( asn1) and the CRISPR/Cas9 mutant lines. The mutant plants showed reduced growth compared to WT with a notable reduction in tiller numbers, suggesting that OsASN1 has an important role in rice development ( Luo et al. 2018) .…”

“…2018) . In this report, we characterized the same T-DNA mutant (indicated as osasn1-1 ) line that was used in a previous report ( Luo et al. 2018) and another T-DNA mutant line ( osasn1-2 ) that was newly isolated by our group.…”

“…2015) . Recently, the analysis of osasn1 mutants generated by T-DNA and CRISPR-Cas9 showed a reduced growth compared to wild type (WT), with a notable reduction in tiller numbers, suggesting that OsASN1 has an important role in rice development ( Luo et al. 2018) .…”