| Summary: | Salinity stress is one of the most prominent abiotic stresses that negatively affect crop production. Transcription factors (TFs) are involved in the absorption, transport, or compartmentation of sodium (Na<sup>+</sup>) or potassium (K<sup>+</sup>) to resist salt stress. The basic helix–loop–helix (bHLH) is a TF gene family critical for plant growth and stress responses, including salinity. Herein, we used the CRISPR/Cas9 strategy to generate the gene editing mutant to investigate the role of <i>OsbHLH024</i> in rice under salt stress. The A nucleotide base deletion was identified in the <i>osbhlh024</i> mutant (A91). Exposure of the A91 under salt stress resulted in a significant increase in the shoot weight, the total chlorophyll content, and the chlorophyll fluorescence. Moreover, high antioxidant activities coincided with less reactive oxygen species (ROS) and stabilized levels of MDA in the A91. This better control of oxidative stress was accompanied by fewer Na<sup>+</sup> but more K<sup>+</sup>, and a balanced level of Ca<sup>2+</sup>, Zn<sup>2+</sup>, and Mg<sup>2+</sup> in the shoot and root of the A91, allowing it to withstand salt stress. Furthermore, the A91 also presented a significantly up-regulated expression of the ion transporter genes (<i>OsHKT1;3</i>, <i>OsHAK7</i>, and <i>OsSOS1</i>) in the shoot when exposed to salt stress. These findings imply that the <i>OsbHLH024</i> might play the role of a negative regulator of salt stress, which will help to understand better the molecular basis of rice production improvement under salt stress.
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