Comparative analysis of TaPHT1;9 function using CRISPR-edited mutants, ectopic transgenic plants and their wild types under soil conditions

Inorganic phosphate (Pi) deficiency is one of the major constraints on wheat growth and development. Identifying the genes conferring Pi efficiency is crucial for improving phosphorus (P) efficiency. Our previous studies showed that TaPHT1;9 is a high-affinity Pi transporter that functions in Pi absorption and transport in wheat seedlings under hydroponic conditions. However, its functions need to be evaluated in complex soil environments. In this study, we aimed to explore its role under soil conditions and reveal its potential for use in the breeding of Pi-efficient wheat cultivars.

CRISPR-edited TaPHT1;9 wheat mutants and TaPHT1;9 ectopic expression transgenic rice plants were cultivated in soils with different Pi supply treatments. The grain yield, biomass, P concentration and P utilization efficiency (PUE) were measured and calculated.

CRISPR-edited homozygous TaPHT1;9-A/B/D wheat mutants were screened and identified. Under low Pi supplies (0 and 5 mg kg⁻¹ P/pot), the grain yields, P accumulations and PUEs were significantly lower than those in the wild-type (WT) control, and the reduced yields were primarily attributed to the decreases in both grain number per spike and 1000-grain weight. The TaPHT1;9-ectopic expression transgenic rice plants exhibited the opposite results, and their grain yields, P accumulations and PUEs were significantly greater than those of the WT plants under insufficient Pi supply conditions.

TaPHT1;9 plays a vital role in Pi utilization under soil conditions; thus, it is considered a candidate target gene for improving crop PUE.