Genome-Wide Identification of the LsaPHR1 Gene Family and Preliminary Functional Validation of LsaPHR1.1 in Phosphorus Tolerance in Lactuca sativa

Phosphorus (P) is a limiting nutrient for plant growth and productivity. Improving P use efficiency is important for crop production. In <i>Lactuca sativa</i> (lettuce), five phosphate starvation response 1 (<i>PHR1</i>) genes were identified and characterized through a bioinformatics approach. The expression patterns of <i>LsaPHR1</i>s were examined using qRT-PCR under various treatments, including devoid phosphorus (DP), low phosphorus (LP), high phosphorus (HP), darkness, ABA, IAA, and MeJA. The results indicate that <i>LsaPHR1</i>s in lettuce responded to phosphorus stress, hormones, and darkness. Furthermore, we engineered <i>LsaPHR1.1</i> knock-out mutants via CRISPR/Cas9-mediated genome editing. Then, the mutants were subjected to phosphorus stress (DP, LP, and HP). In contrast to WT, the mutants improved nitrate and ammonium contents, increased antioxidant enzyme activity, and elevated antioxidant and chlorophyll contents. Our results offer a potential strategy for improving phosphorus stress tolerance in lettuce, which holds great significance for maintaining yield and quality.