Soybean PHR1-regulated low phosphorus-responsiveGmRALF22increases uptake of phosphate via stimulatingGmPTs expression

Abstract

Phosphorus (P) is one of essential macronutrients for plant growth and development. Rapid Alkalization Factors (RALFs) play crucial roles in plant responses to nutrient stresses, however, the functions ofGlycine maxRALFs (GmRALFs) under low P (LP) stress remain elusive. In this study, we first identified 27GmRALFs in soybean, then we revealed thatGmRALF10, GmRALF11, andGmRALF22are induced in both roots and leaves, while onlyGmRALF5,GmRALF6, andGmRALF25are up-regulated in leaves in LP conditions. Furthermore,GmRALF22was found to be the target gene of transcription factorGmPHR1,which binds the P1BScis-element in the promoter ofGmRALF22via electrophoretic mobility shift assay (EMSA) and DUAL-LUC experiment. Colonization ofBacillus subtilisthat deliver GmRALF22 increases the expression of high affinity phosphate (Pi) transporter geneGmPT2, GmPT11, GmPT13andGmPT14, thus increases the total amount of dry matter and soluble Pi in soybean. RNA-sequencing uncovered that GmRALF22 alleviates LP stress by regulating the expression of JA-, SA- and immune-related genes. Finally, we verified that GmRALF22 is dependent on FERONIA to promote Arabidopsis primary root growth under LP conditions. In summary,GmPHR1-GmRALF22module positively regulates soybean’s tolerance to LP.HighlightsSoybean genome has 27GmRALFs.GmRALF5,GmRALF6, GmRALF10,GmRALF11,GmRALF22andGmRALF25are induced in low phosphorus (LP).GmPHR1 directly regulate the transcription ofGmRALF22 viabinding the promoter P1BScis-element.Secretion of GmRALF22 protein byBacillus subtilispromoted soybean growth under LP conditions by improving soybean P nutrition through increased expression of high affinity phosphate (Pi) transporter gene.GmRALF22 regulates soybean P nutrition by JA-, SA- and immune-related genes expression at transcriptome level. That application of GmRALF22 promoted primary root growth in Arabidopsis in LP is dependent on FER receptor.