Strigolactone mediates moso bamboo root response to phosphate stress

Moso bamboo ( Phyllostachys edulis ) grows in soils with widespread phosphate (Pi) deficiency, resulting in low shoot yield. While it also suffers from high Pi due to heavy fertilization, which causes the degradation of bamboo forest. A novel plant hormone, strigolactone (SL), plays a key role in root growth and development under Pi stress, but its regulatory mechanism has not been systematically reported. Our study investigated SL-mediated mechanism in response to Pi stress in moso bamboo. We compared the root growth under low, sufficient and high Pi, and analyzed the temporary trends of gene expression in primary root tip region and lateral root primordium zone. The effects of SL-analog (GR24) and SL-inhibitor (TIS108) on root architecture at low and high Pi were evaluated. SL biosynthesis and signaling are the main pathways of root response to Pi stress. With the decrease of Pi level, 5-deoxystrigol and strigol in the root exudates increase significantly. Under low Pi, SL is indispensable for the maintenance of root cell morphology, and promotes primary root elongation and reduces lateral root formation by upregulating the expression of phosphorous starvation response genes and downregulating the expression of abscisic acid response genes. The absence of SL at high Pi releases the inhibition of ethylene responsive genes’ expression to inhibit root elongation and promote branching. In general, SL mediates the response of bamboo roots to Pi stress by regulating its biosynthesis and signal transduction and influencing other hormone pathways.