Revealing the underlying molecular basis of phosphorus recycling in the green manure crop Astragalus sinicus

The use of green manure as an organic fertilizer to main crops has been widely proposed as a sustainable method for ecological restoration and increasing soil fertility in degraded environments. Given the increasing excessive application of phosphate (Pi) fertilizer and the accompanying risk of environmental pollution, a strategy is required to increase the Pi absorption efficiency of green manures with nitrogen (N)-fixing ability and further improve N–P recycling and the soil remediation effect in agroecosystems. Leguminous crops, such as milk vetch ( Astragalus sinicus ), are the most widely used green manure plant species. In this study, through physiological assessments of different Astragalus sinicus cultivars under Pi starvation, an elite variety, Astragalus sinicus Xinzi-1 was identified, which showed high tolerance to Pi starvation and approximately 25%–60% higher Pi content than other varieties. Comparative transcriptome analysis showed that, upon Pi starvation, the expression profiles of core genes involved in Pi transport and signaling were globally and dramatically altered in Xinzi-1. Specifically, the expression of genes encoding Pi uptake transporters and acid phosphatases in Xinzi-1 were remarkably induced under Pi deficient condition. The results showed that increasing the Pi absorption efficiency of N-fixing green manure can improve the N–P recycling efficiency and soil remediation effect of green manures. This study also provides new insights for future research on appropriate breeding guidance, variety evaluation, and field management of green manures in sustainable agroecosystems. • A. sinicus Xinzi-1 is with high tolerance of Pi starvation and high Pi accumulation. • Spatial-temporal full-length transcriptomic analysis of Xinzi-1 was carried out. • Network of Pi homeostasis was globally altered in Xinzi-1 under Pi starvation. • Highly efficient N–P recycling system between legume green manures and crops was proposed.