SAMS1 stimulates tomato root growth and P availability via activating polyamines and ethylene synergetic signaling under low-P condition

Abstract

Phosphorus (P) utilization by plants is low, which limits crop yields and causes environmental pollution. SAMS1 controls polyamines and ethylene synthesis, and actively responds to various biotic and abiotic stresses. However, how SAMS1 regulates plant P efficiency remains unclear. This study showed that SAMS1-overexpressing improves tomato P efficiency. As a result, overexpression of SAMS1 reduced the accumulation of putrescine and, which induced H2O2 by promoting the conversion of putrescine to spermidine/spermine. This not only facilitated the occurrence of lateral roots under low-P conditions but also promoted the continuous elongation of lateral roots, forming the low-P adaptive root morphological characteristics in tomato plants. In addition to morphological regulation, SAMS1 also promoted root H+-ATPase activity and H+ secretion through polyamines and ethylene signals, enhancing P absorption. However, the phosphatase activity, reutilization of cell wall P, and its distribution to the root was only induced by SAMS1-mediated ethylene signal. Field experiments showed that using SAMS1-overexpressing transgenic rootstocks significantly reduced the input of P fertilizer, promoted plant growth and yield. Together, SAMS1 can promote tomato root growth and P utilization by activating synergistic signals of PAs and Eth.