Lhca4 Maintaining Photochemical Efficiency and ROS Homeostasis Contributes to Rice Salt Tolerance

Rice (Oryza sativa L.), a staple food for more than half of the global population, is moderately salt-sensitive and increasingly threatened by soil salinization. Deciphering the genetic mechanisms of salt tolerance (ST) is pivotal for accelerating genetic improvement of ST by rice molecular breeding and safeguarding global food security.

A quantitative trait locus for rice ST, qRLS8, was mapped using a BC₂F₇ backcross introgression line population derived from the cross between Minghui 63 and 02428. Combined with transcriptome analysis, Lhca4, encoding a subunit of the light-harvesting complex, was identified as the candidate gene of qRLS8. Lhca4 positively regulates rice ST at seedling stage based on the phenotypic verification using knockout and overexpression transgenic lines of Lhca4. Overexpression of Lhca4 increased the activities of superoxide dismutase and peroxidase, and decreased the accumulation of H₂O₂ and O₂^-, holding a high photochemical efficiency under salt stress conditions. In contrast, knockout of Lhca4 increased accumulation of reactive oxygen species (ROS) in rice, resulting in disruption of the chloroplast lamellae and a decrease in photosynthetic efficiency. Transcriptome analysis revealed that Lhca4 mediated salt stress response pathway involved in metabolic regulation, enzyme activity regulation, and antioxidant regulation.

Lhca4 confers rice ST by preserving chloroplast integrity, maintaining photochemical efficiency, and systemically modulating ROS homeostasis through enhancing antioxidant defense system. These findings provide a valuable gene target for the development of salt-tolerant rice varieties without compromising photosynthetic capacity.